Taking the crankshaft of large reciprocating compressor as a research object, Box-Behnken experimental design is used to optimize the crankshaft structure, so as to reduce the torsional amplitude of crankshaft system and the torsional angle of free end. Firstly, Taguchi design test method is used to select the significant factors which have great influence on the strength and torsion performance of the crankshaft system from the design parameters of multiple crankshaft structures. And then, Box-Behnken experimental design method is used to optimize the significant factors, and the final optimization value of crankshaft structural design parameters is obtained. Finally, by optimizing the crank thickness, the center disk thickness and the length of the large end crank pin of eight fully balanced crankshafts, it is shown that the peak stress and the free end torsion angle are reduced by 22.4% and 4.5% respectively in one cycle compared with those before optimization, which indicates that the strength of the crankshaft system is increased and the torsion amplitude is reduced after optimization. The research results provide effective theory and evidence for the research and design of large multi-row crankshaft.