The traditional calculation of ship lock capacity is based on the subjective result of simple manual permutation，which cannot reflect the dynamic process of ships arriving at the lock at random，nor does it reflect the service level of the ship lock. To comprehensively reflect and reasonably evaluate the impact of random arrival of ships and operation scheduling of ship lock capacity，this paper carries out a simulation study on the ship lock capacity. The ship random arrival process is automatic generated according to the proportion of ship types in the channel. Scheduling by the optimal matching permutation strategy and sequential service permutation strategy is carried out. Two classical operational research models（two-dimensional packing problem and knapsack problem） are used to calculate the combination of passing ships and the gross tonnage of one-time passing. Based on this theory，a simulation calculation software for the ship lock capacity is developed，which can better make up for the shortcomings of the existing calculation methods.