The effect of carpooling is very significant in many aspects such as reducing the cost of logistics and traffic congestion. In this paper, a clustering heuristic strategy based on matching degree is introduced to assign the demand of services to one specific vehicle. In a single vehicle problem, a prior clustering idea to reduce the number of insertion operation is induced which may improve the efficiency of the algorithm. Additionally, migration operator is proposed to improve the success rate of matching and to reduce total costs. Real examples show that the algorithm not only cuts down a vehicle's idling rate, but also reduces the vehicle operation cost to some degree.