The research of urban rail transit dynamic accessibility and last train timetable is the basis for optimizing the transfer between last trains in different lines and maximizing transportation benefits． First，urban rail transit dy-namic accessibility is defined from three dimensions such as stations，transit lines，and the whole network，based on the static network topology and dynamic passenger flow． Second，dynamic accessibility indicators of Guangzhou rail transit network is evaluated through assigning the dynamic passenger flow data to the whole network． Finally，aiming at maximizing dynamic accessibility，a last train optimizing model is proposed，taking into consideration the departure time constraint of the last trains for all lines，and a genetic algorithm is applied to solve the optimization problem． Taking Guangzhou subway network for the case study，the analysis shows that static accessibility and dy-namic accessibility of Guangzhou rail transit network increased by 20. 29% and 10. 97percentage points respectively after the adjustment of the last train timetable，which indicates that the optimized last train timetable can effectively improve transport capacity．