Abstract: A quality of service (QoS) routing optimization algorithm based on differentiated services (DiffServ) is proposed. This algorithm improves QoS guarantees of wireless multimedia sensor network (WMSN) in two ways: selecting path through different probabilities when transmitting different kinds of packages, at the same time, adopting a preemptive priority queuing model for the packages in the sensor nodes. In simulation, we compared the method with SAR algorithm in various ways, including supporting capacity of network scale, transmission delay of data packages, energy efficiency and network life. Experimental results show that as far as above-mentioned indexes, the algorithm is superior to the SAR algorithm and the algorithm can guarantee QoS requirement of various data packages with different types.