The utility model relates to a sampling of contravariant output transformer excitation current and current -limiting protection device, including a contravariant module, the contravariant module is a full -bridge contravariant module Q1 to fourth power switch pipe Q4 is managed to first power switch, the device still includes an excitation current sampling circuit, a comparison circuit and a protection circuit, excitation current sampling circuit's an input and a contravariant output transformer link to each other, are used for sampling contravariant output transformer's excitation current, excitation current sampling circuit's output is connected to comparison circuit's positive input terminal, comparison circuit's a negative entry termination reference level, comparison circuit's output is connected to the input of protection circuit, the output of protection circuit is connected to the contravariant module. The utility model discloses can carry out the current -limiting alone to excitation current, avoid positive half -wave or the burden half -wave current too big and cause output transformer saturation and damage contravariant module power device.