Hot cathode low-pressure mercury lamp can be used as the light source for cold atomic absorption mercury detector, but the light intensity has problems of large fluctuation and serious drift when the lamp is driven by the conventional electronic ballast. This condition cannot meet the low detection limit requirement. Therefore, a lamp drive and light intensity stabilization method is proposed in this paper. To realize warm-up start and maintain normal illumination of lamp, a self-excited current-fed push-pull resonant inverter was constructed, and the parameters were designed according to the equivalent circuit model. To improve the light intensity stability, a closed-loop control system with light intensity feedback mode was established, and the frequency domain of the system was analyzed and optimized. The feasibility of circuit was verified by simulation. The stability of light intensity was tested by a cold atomic absorption mercury detector. The results show that the mercury light intensity fluctuation is less than 0.15‰, and the baseline drift is less than 0.06‰ within 50 min.