This paper explores the travel decision-making process of healthcare behavior of urban elderly under different temporal and spatial constraints. Firstly, based on time geography, a two-dimensional space-time trip chain is applied and the concept of healthcare constraint degree (HCD) is proposed. Then, the elderly's medical treatment activities are divided into two categories: strong constraint activity and weak constraint activity, based on 625 samples in Kunming, China. Lastly, an improved multinomial logit model is adopted to determine the significant factors affecting the travel mode choice of these two types of activities. The results show that the travel mode choice of the elderly to healthcare facilities is not the same under different spatio-temporal constraints: strong constraint activity is mainly affected by external factors (such as travel time, travel distance, bus station distance and walking accessibility), whereas weak constraint activity is influenced by internal family factors (such as car pick-up, accompanied by family, and the number of family members with a driver's license). These findings present a new perspective for understanding the healthcare behavior of the elderly and provide a convincing support for the formulation of urban transportation planning policies.