Research purposes ： The overall efficiency of urban rail transit construction and operation of the whole life cycle is directly related to the rationality of networl^ scale，and the rationality is the core index of rail transit networl^ plan. Aiming at the problem that there are obvious differences，one - sided interpretation，and difficult combination in different network scale calculation results，the model of the reasonable scale of rail transit network calculation based on entropy weight is put forward. Research conclusions ：( 1) Based on summarizing the concept of the existed urban rail transit network reasonable scale， further deepening and clarifying the specific meaning and external performance of rational scale. (2) Based on the service level analysis of network scale， the results of the three methods are given a treatment of valuation by using information entropy，and thereasonablevalueof network scaleis determined amply，effectively enhancing therationality of network scale. ( 3 ) The model is applied on the case of network scale of cityrail transit studyin Chongqing，and the results show that tlie reasonable scale value should be 570. 61km in 2020，so there is still tlie space of adjustment and optimization in the actual plan. (4) The model can analyze and calculate the comprehensive value of each urban rail transit network reasonable scale，providing the theoretical support for the urban rail transit network plan in China.