A method using an averaging technique for the analysis and evaluation of real quasi-resonant converters (QRC's) is proposed in this paper. To reduce the great difference between the real characteristics and those of ideal circuits, a modeling technique is developed by considering the effect of parasitic power losses. Then, using the averaging approach reasonably simplifies the process of solving equations to obtain the steady-state solutions of state variables. Also, an updating algorithm is constructed to take all the power losses such as core losses, which are often absent in the conventional analysis, into account to improve the accuracy of the steady-state solutions. By these efforts, the evaluation of characteristics for QRC's is realized.