Based on the discrete dynamic model， the convergence and accuracy of power hardware-in-the-loop simulation（PHILS） are studied. PHILS works as a numerical approach， and by analyzing errors of the discrete dynamic model， the convergence of PHILS is proved. Because of convergence， the accuracy of PHILS is determined by the delayed system to which PHILS converges. The theoretical solution and the interface power conversion relationship for AC steady-state solution of PHILS are derived. To verify the theoretical conclusions， a PHILS experiment of a resistance circuit is implemented， and the experimental results are consistent with the theoretical analysis.