Abstract: Large-scale gas reciprocating compressor needs optimizing many times in the process of design due to its complex structure. However, only the demand of individual component is taken into consideration during the optimization design, and the demand of other components and the overall performance of the compressor are not considered sufficiently in the optimization result. As a result, some problems occur frequently, such as component rework and poor overall quality. To solve these problems, a reliability evaluation method of optimization design of compressor based on Hazard and Operability Analysis(HAZOP)was proposed in this paper. In this method, compressor hierarchical structure is constructed, the transmission process of design change information between unit interfaces is investigated, reliability evaluation is carried out on the influence consequences in the information transmission path by HAZOP, and the reasonable countermeasures are prepared in the design stage. This method was applied to the design optimization of the crank shaft of one certain compressor. It is indicated that on the premise of ensuring the reliability of the compressor, this method optimizes the diameters of the crank shaft king journal and crank pin from 182.8 mm to 177.8 mm. In conclusion, this reliability evaluation method for optimization design of compressor based on HAZOP considers fully the effects of design information change on the other units and the overall performance of the compressor, so it improves the reliability of compressors.