Abstract: In block assembling,the different welding position and welding types make the work time of block assembling different.To determin the work time of block assembling exactly and improve the efficiency of the assembly,the worker can use the model information in the design to determine the different welding time according to the different welding position and welding types.To shorten the time of block construction,by optimizing block division,the welding time is set as the objective function,the genetic algorithm and production model are used to optimize the assembling hierarchy structures.By generating the different assembly plan schemes in assembling hierarchy structures,designing the effective genetic operator and determining the genetic algorithm parameters and using the objective function to evaluate the optimization results,this paper gets an optimization system of ship block assembling.