Urban park accessibility is an important indicator to measure the level of urban modern development, and the harmonious relationships between people and land. It is meaningful for efficiently increasing urban park accessibility, fully providing services functions of urban park and promoting healthy development of cities to understand objective influencing factors of urban park accessibility and its extent of impact. The service area and service efficiency of urban parks in three-ring area of Shenyang City were evaluated basing on ArcGIS 9.3 software platform and network analysis methods. The regularity of the service area and service efficiency of urban parks changing with the urban park area, urban park shape and road network density were analyzed. The results showed that urban park area had significant positive correlation with service area and significant negative correlation with service efficiency. Urban park shape had significant positive correlation with service area and service efficiency. Road network density had significant negative correlation with service area of urban parks, but had no significant correlation with service efficiency. Based on the extent of impact on urban park service area, the importance of three influencing factors was in the order of urban park area> road network density > urban park shape. Based on the extent of impact on urban park service efficiency, the importance of three influencing factors was in the order of urban park area> urban park shape > road network density. Urban park area was the most important influencing factor for the service area and service efficiency of urban parks.