The invention provides a method and a device for evaluating service quality. By counting the sum of packet loss retransmission time delays caused by each retransmission data packet in an appointed time on the connection established at a service sending party and a service receiving part, the quality of service developed on the connection is evaluated; whether the actual time lasting from requesting the service to obtaining the content of the requested service by a user under various application scenes is larger than expected time is mainly determined by the packet loss retransmission time delays, namely the service quality of mobile data service is mainly related to packet loss retransmission time delay, so that, based on the sum of the packet loss retransmission time delays caused by retransmission data packets, the service quality of the mobile data service in the aspect of service speed can be conveniently and efficiently evaluated, and the technical problem in the prior art that the evaluation efficiency of the service quality of the mobile data service in the aspect of service speed is too low is solved.