This paper describes the numerical circuit analysis of a magnetic oscillation direct current/alternating current (dc-ac) power converter using a magnetic control device called a bridge-connected magnetic circuit. The converter can supply electric power to an ac-voltage source such as a line electric power source and can control the output electric power by using the small dc-current that flows through the control winding of the bridge-connected magnetic circuit. A simulation model of the bridge-connected magnetic circuit and a simulation circuit of the dc-ac converter based on a general purpose circuit simulation program called “SPICE” are proposed for the quantitative analysis of the dc-ac converter. The fundamental characteristics of the dc-ac converter were calculated using SPICE. Comparisons between the simulation results and the experimental ones are presented in this paper.