Vegetation is an essential natural feature in urban greening and a crucial indicator of an advanced city; it also enhances people’s quality of life. The maintenance of vegetation with wide coverage in an urban park is crucial. However, few studies have discussed the effects of vegetation quality and quantity on human health. The current study discusses how the quantity and quality of park vegetation affect people’s behavior pertaining to park visitation (i.e., frequency and duration of park visits) and explores the effect of vegetation on people’s physical activity and life satisfaction. A total of nine parks were included, and 730 participants were recruited to answer a questionnaire concerning perceived vegetation conditions, park visit behaviors, physical activity, and life satisfaction. The results indicate that the perceived maintenance of vegetation significantly and positively influences the frequency and duration of people’s park visits, which in turn exhibit a positive association with their physical activity and life satisfaction. People’s overall satisfaction with park vegetation also positively affects their physical activity and life satisfaction. The results revealed the key roles of plant design, maintenance, and management in increasing the frequency and duration of park visits, which enhance people’s physical activity and health.