The stability of the current source is one of the key factors affecting the resolution and imaging quality of the high stability electromagnetic lens. As a feedback element of the current source, the stability of the reference resistance directly affects the stability of the current source. In order to improve the stability of the reference resistance, the temperature characteristics of the reference resistance and NTC (Negative Temperature Coefficient) thermistor are analyzed, and a circuit structure for temperature compensation of the reference resistance by NTC thermistor is proposed. Taking Pt100 resistance as the reference resistance, the performance of the circuit structure is analyzed. The results show that the stability of the equivalent reference resistance obtained by compensation is more than 10 times higher than that of the reference resistance.