Abstract: With some particular advantages the oscillatory De-Qing circuit now is widelyused. However its design is very complex. By means of a quantitative analysis forthis circuit a group of design formulas are obtained. According to these designformulas we can easily determine the maximum allowable charging inductance L_c,the De-Qing network resistance R and capacitance C, if the PFN capacitance C_N,the maximum pulse frequency F_(max), and percentage regulation η are given. Simple and direct formulas for specific situation are listed. Finally, we givea design example and compare it with experimental result which shows that thedesign method is feasible and reliable.