The invention discloses a novel 
urban rail transit vehicle air-conditioning control method based on changes of outside temperature and passenger capacity. The method includes the following steps that S1, multiple 
linear regression is conducted according to data obtained by calculating the 
air temperature outside a vehicle, the passenger capacity of the vehicle and condition parameters of clothes wearing 
thermal resistance of passengers, and then a two-variable linear in-car 
temperature control model based on the outside temperature and the passenger capacity and meeting the equation T_in=kl*T_out-k2*n+k3 can be obtained; S2, real-time temperature signals outside the vehicle and in-
car passenger capacity signals are collected and are led into the 
temperature control model in the S1, and then an in-car 
target control temperature is obtained; S3, real-time temperature values of multiple areas in the vehicle are collected and averaged to obtain an average value, then the average value is compared with the in-car 
target control temperature obtained in the S2, the working state of a vehicle air-conditioning unit is adjusted automatically according to a comparison result, next the output 
refrigeration amount of the air-conditioning unit is adjusted, and finally automatic adjustment and control over the in-car temperature is achieved. According to the method, the actual passenger capacity of the vehicle and environment temperature signals outside the vehicle are led simultaneously to serve as variable calculation parameters of the in-car 
target control temperature, so the in-car target control temperature better meeting passenger capacity 
thermal comfort requirements can be calculated comprehensively and accurately.