Abstract: Direct-quadrature(D-Q) coordinate transformation is an effective circuit modeling method which is often used in three-phase circuit equivalent transformation. In this paper, a method which constructs a virtual orthogonal circuit is used to derivate the D-Q equivalent circuit of the single-phase parallel resonant converter in D-Q rotating coordinate. The transfer function of the equivalent circuit is solved. And it is verified that the derived D-Q equivalent circuit can accurately represent the original converter circuit by simulation. Based on this conclusion, by the transfer function of the D-Q equivalent circuit, the output LC filter parameters of a single-phase parallel resonant converter is designed, meeting the output voltage pulse less than 50 s edge, less than 5% overshoot, less than 100 s settling time and less than 5% ripple. It is proved that the method used to design the parallel resonant converter output LC filter parameters is feasible.