Aiming at the problem that the data traffic will be delayed at relays and the delay requirement of it may not be satisfied, a relay selection model with the consideration of the relaying delay is established in the two hop DF cooperative communication systems. On this basis, a new relay selection method considering the relaying delay of the service is proposed. The performances of the proposed method are also analyzed. First of all, the probability density function (PDF) of the relaying delay at the relays is derived. Thereafter, the analytical expressions of the average system capacity and outage probability are obtained. The simulation results are in accordance with the theory accurately and also verify that the proposed method can effectively reduce the average delay at relays while guaranteeing a considerable data rate.