A distribution network for one warehouse and multiple retailers is considered in this paper. The amount of vehicle is viewed upon as an operational variable without upper bound, which is known as flexible vehicle. According to whether the truck is full, different strategies are adopted, viz. direct shipment and peddling shipment. Using the peddling shipment strategy, a model named WVRP with weight coefficient is built. Distinguished from many other models, the demand of each retailer is also important factor to be considered when routing schedule is made. The retailers with larger demands have priority to be visited earlier. Finally, a genetic algorithm named PB- GA using a special partition method is proposed to solve this model, detailed comparison is made with usual heuristic for vehicle routing problem.[