Credible capacity evaluation of active distribution network ( ADN) can make full use of distributed generations ( DGs) ，which provides valid reference for the optimal allocation of ADN． The credible capacity of ADN is defined as the payload capacity of DGs，and the evaluation model is established based on reliability indexes． Different situation with considering the fault of lines are classified and calculated on the basis of Monte Carlo simulation． The load adjustment steps are calculated by the method which is based on relative growth of loads． Finally，the credible capacity of ADN is calculated using the midpoint segmentation iteration method． The feasibility and validity of the proposed method are verified in IEEE 33 nodes system． In the simulation it can find that the rated power of wind powers has a greater influence on the calculation results of credible capacity when DGs parameters and reliability indexes are changed．