Abstract: Urban parks play an important role in improving urban environments and public health. Visual green index(VGI) measures the quantity of green spaces based on human vision, and its effect on people's physical and mental health must be explored further. The research results provide suggestions for the planning, construction, and optimization of urban green spaces. Based on real images of urban parks, the influence of urban park environment (based on VGI) on human physical and mental health was explored through VR technology, POMS scale and semantic analysis scale were used as the psychological evaluation indicators, and skin conductance values as the physiological evaluation indicator.
　　In this study, four urban parks in Hangzhou City of different types and sizes were chosen as the research samples, including Huagang Guanyu, Quyuan Fenghe, Fengtan Urban Cultural Park, and Jialuyuan Park. The panoramic images were collected on site by the grid method, and VGI was calculated using the pixel calculation method. The field survey results showed that the overall VGI in the four urban parks was relatively high, with an average value of 46%. Moreover, greening rate and maintenance were both good.
　　Based on the VR experiment, some conclusions were drawn: (1) The static VR experience of green space in urban parks can help individuals relax, increasing positive emotions and decreasing negative ones. Environments with low VGI (0%) can significantly inhibit psychological recovery of individuals. (2) Under experimental conditions (10%~66%), the degree of individuals' psychological and physiological recovery positively correlated with the VGI of urban parks. Regarding the psychological index (scale scores), individuals' positive emotion scores increased significantly with the increase of VGI in urban park spaces, while the negative emotion scores decreased. The results of physiological indexes (skin conductance rate) showed that when the VGI was 35~66%, the skin conductance rates of individuals tended to be stable. (3) When the VGI was 25%, many factors had collaborative influences on the physical and mental recovery of individuals, such as the water areas, openness of spaces, hard site areas, and so on. When the VGI was higher than 35%, it was the dominant environmental factor that influenced the physical and psychological health of individuals. (4) The environment with higher VGI (>35%) promoted physical and psychological recovery of individuals more effectively. According to the correlation and dispersion analysis between psychological (semantic analysis scales) and physiological indexes (skin conductance rate), individuals achieved a relatively uniform physiological recovery effect in environments with a high VGI. 
　　This test of psychological and physiological indicators proves that green environments in urban parks can positively promote psychological and physiological health. With every increase in the environmental VGI, this effect becomes more significant. Scenes with a high VGI (>50%) created the most prominent effect of psychological and psychological recovery. These research conclusions can guide planning, construction, and management of urban park green spaces. In urban park planning, the design of crowd activity spaces should increase the environmental VGI (>35%). For example, increasing grass, trees, and other plants can enclose the site, thus decreasing the openness of the space. It is also suggested to construct pools, streams, and lake landscapes when increasing visual green rate is not possible due to site limitations. This can increase the proportion of environmental blue space and also promote human health to some extent.

Key words: urban park, visual green index(VGI), physical and mental health, Hangzhou 

摘要： 绿视率为城市公园环境评估的重要指标，其对人体身心健康影响的效应有待深入探讨，研究结果可为城市绿地规划建设及优化提供参考。基于城市公园实景影像，通过VR技术、利用POMS量表与语义分析量表评分作为心理评估指标，皮电信号值作为生理评估指标，探究基于绿视率的城市公园环境对人体身心健康的影响机制。结果表明：（1）城市公园绿色空间静态VR体验能使个体精神放松，增加积极情绪，减少消极情绪；（2）在实验条件下（绿视率范围10%～66%），随着场景绿视率的增加，个体心理、生理恢复愈加显著；（3）当环境绿视率低于35%时，其对个体的身心恢复受多因素协同影响，如水体面积、空间开敞度、硬质场地面积等；当绿视率值高于35%时，绿视率为环境对个体身心影响的主导因子。

关键词: 城市公园, 绿视率, 身心健康, 杭州