Abstract: In view of the continuous upgrading of performance indicators of medium speed marine diesel engine and the demand target that the high standard of crankshaft manufacturing makes the crankshaft processing technology more complex, a special crankshaft lathe fixture is designed. The fixture can meet the processing of connecting rod journal and crankshaft crank arm at the same time, and the fixture is suitable for a variety of models, with certain versatility. It only needs to match the counterweight and adjust the indexing according to the crankshaft model. The existing non-circular polishing technology is not conducive to ensuring the cylindricity of the crankshaft journal. At the same time, non-circular polishing is difficult to achieve the ideal contact effect between the crankshaft journal and the bearing bush, which is not conducive to the generation of lubricating oil film. A special polishing device is designed to overcome the problem of insufficient contact area between the journal and the abrasive belt in the polishing process. At the same time, the whole polishing process is divided into two processes, coarse and fine, which realizes the whole round polishing and provides the detection scheme of the contact area of the journal. The crankshaft assembly is approximately simplified as a two degree of freedom vibration system on the elastic support, and its dynamic balance is analyzed.