It is very important to forecast the fatigue crack development upon welded girder of bridge crane during use. When it happens, it will have a lot of clout with performance of enterprises. For security purpose in use, ANFIS model is built to predict the length of the fatigue crack extension about welded girder of bridge crane. Membership function is adjusted according to inputs and outputs of fuzzy reasoning, and appropriate fuzzy regulation numbers are chosen. The model which is closest to the real development of fatigue crack is built with the help of the If-Then rules. According to the result from the fatigue experiment of the welded girder of bridge crane, ANFIS model, ANN model and Three Order Spline Interpolation model are respectively built. After analysis and verification, it is obvious that ANFIS model is more accurate and feasible.