According to meet the demand of high precision current sampling in complex current environment, a TMR (tunnel magnetoresistance) anti DC current sensor is designed. in this paper. The cause of over-tolerance of traditional current transformer under DC component is analyzed theoretically, and the relationship between the ratio difference and angle difference and DC component is given. The working principle of TMR anti DC current sensor is described, and the relationship between output current Is and input current Ip is deduced. The tests show: Under the condition of half-wave rectification load, the maximum ratio difference of TMR current sensor is -0.23% , the maximum angle difference is 4.92′ , and the maximum error of TMR current sensor is -1.77% in the measuring range of (0.5~60) A, the error is 9.4% of the metering error of the three-phase direct access watt-hour meter with traditional anti-dc current transformer. The current sensor has a good application prospect in DC distribution network and electric vehicle charging metering.