The invention provides an optimal design method of a sequence valve of a steam turbine with four high governing valves. The optimal design method of the sequence valve of the steam turbine with the four high governing valves comprises the following steps that S1, six opening sequences based on the four high governing valves are listed; S2, geometric models of the four high governing valves are established, and the four geometric models are guided into hydrodynamics analysis software to be subjected to pretreatment; S3, finite element models of the four high governing valves under six valve sequence combinations are solved; S4, evaluation parameter indexes are extracted from finite element analysis software so as to analyze and compare the six valve sequence combinations and governing stageblade stress under different working conditions; and S5, an optimal valve sequence combination is given according to comparative analysis in the step S4, experiment research is carried out on the premise of theoretical calculation, so that the precision and the accuracy of theoretical calculation are verified. According to the optimal design method, the problems of faults of the steam turbine andthe affected service life of the steam turbine caused by the unreasonable opening sequence of the steam turbine sequence valve in the prior art are effectively solved.