With the development of next generation network (NGN), reasonable service quality evaluation is essential in network management. Based on NGN service characteristics, this article presents a comprehensive service quality evaluation system from two perspectives: quantitative and qualitative. From the quantitative point of view, this article brings forward the normalized service level achievement function (NSLA function) at technical layer. Also, with mean opinion score (MOS) mode, it proposes customer satisfaction assessment methods at customer perception layer. From the qualitative perspective, a hierarchical model is established, which forms mapping relations from the upper customer perception to the lower service quality parameters, and then the influence of different service parameters on customer satisfaction degree can be denoted by the fuzzy analysis hierarchy process (FAHP) algorithm. Quantitative and qualitative evaluations together form a comprehensive solution which is universal, customer-oriented and flexible. Demonstrated by the representative voice service, the proposed system is proved reliable and applicable to service evaluation in NGN.