The blank of heavy pressure vessel is forged directly, so its machined surface is very terrible. Because of its very large size and weight, it costs very much time and expenses cost, lots of tools and activity float to turn it during the period of rough machining. This paper describes the machining characteristic of the machining difficult points of heavy pressure vessel in China. Through analyzing the processing difficulties and utilizing the methods of experimentation and manufacture, it discussed on the choice of cutting parameters, tool structure and the optimization of tool material and so on. Then the effective measures of rough machining efficiency were constituted. Last, the processing plan which is summarized turns into the guidance of the heavy pressure vessel in actual production period.