Large crawler cranes are the core equipment for major engineering construction, widely used in large-scale lifting operations, in which the machining accuracy of the long boring of the cross girder platform directly affects the life of large crawler cranes and the smoothness of operation. In order to improve the machining accuracy of the cross girder platform, firstly, the processing technology of the cross girder platform is analyzed, and problems such as large structural dimensions and large difficulty in long boring processing are identified. Then formulated the specific implementation plan of the long boring machining process of the crossbeam platform. Finally, measure and analyze the coaxiality of the machined long boring, through the measurement of the process to meet the requirements.