The work aims to create a mathematical model for optimization of storage location assignment problem (SLAP) so as to reduce operation time and distance of the stocker in automobile harness warehouse and improve order handling efficiency. According to the actual conditions in an automobile harness warehouse, the work analyzed the historical data and simulated the SLAP by the improved genetic algorithm that was developed based on the dedicated storage model. The simulation results indicated that the dedicated storage allocation system outperformed the closest open location, the random storage and the class-based storage method. It reduced the operation time of stacker by 18.8%, 16.9%和35.7% respectively. In conclusion, the dedicated storage model can effectively improve the efficiency of order handling in automobile harness warehouse.