Understanding location-specific travel modes and acceptable travel time to primary healthcare institutions across large regions is important for measuring accessibility and allocation of health resources. However, few studies have either focused on such analysis or provided efficient methods. We developed a framework to understand the diversity of travel modes and acceptable travel time across large regions and chose Inner Mongolia Autonomous Region, China as the study region. Information on health-seeking travel behaviors to primary healthcare institutions was collected using a simple online questionnaire, based on which, Bayesian statistical models were developed and high-resolution maps for travel mode selection and acceptable travel time were produced. Age, gender, occupation, travel time to the nearest urban center, and nighttime light had significant associations with the choice of travel modes. And age, gender, occupation, travel mode, and nighttime light showed significant relationships with levels of the acceptance of travel time. The proportions of travel modes and levels of acceptable travel time show heterogeneous across the study region. Most people chose to walk or travel by bus, with population weighted average proportions 40.59% and 21.11% across the study region, and people in the southeastern part were less tolerable for longer travel time than those in other regions. This study provided a framework to estimate travel modes and acceptable travel time across large regions. The outcomes can provide important information on the assessment of accessibility to primary healthcare services and health resource allocation in Inner Mongolia. •We developed a framework to map travel modes and acceptable travel time to primary healthcare institutions in large regions.•Several factors were identified significantly associated with the choice of travel modes and the acceptable travel time.•High-resolution maps for travel mode selection and acceptable travel time in Inner Mongolia were produced.