The security of differential-phase-shift quantum key distribution with weak coherent states is analyzed synthetically. Also, its security combining with decoy states is reevaluated. The expressions of key generation efficiency are given, respectively. The theoretical results indicate that differential-phase-shift quantum key distribution with decoy states is immune from the photon number splitting attacking and the sequential attacking, and its expression of key generation efficiency is identical with that proposed by Hoi-Kwong et al. The experimental data indicate that the combined system not only achieved longer transmission distance, but also improved the key generation efficiency about an order.