As a key component of pulse power device, the self-breakdown probability of gas switch and the jitter of trigger discharge delay have a crucial impact on the whole pulse power system. Reducing the working coefficient of the switch is beneficial to improve the stability of the switch, but the delay jitter will increase accordingly. Aiming at the application requirements of 10 MA level high-current devices used in magnetically driven experiments, a three-electrode gas switch with high field distortion coefficient and stable operation under low operating coefficient was designed and its performance was studied. The simulated and experimental results show that when the trigger voltage is equal to the charging voltage, the field distortion coefficient is close to 4, and when the switch operating coefficient is higher than 60%, the switch has low delay jitter with the root mean square of less than 3 ns. Combined with the proposed switch, a two-stage Marx energy storage module was designed. When discharged under the condition of charging voltage ±50 kV and short circuit, its peak discharge current can reach 150 kA with a period of 2 μs. After thousands of discharge experiments, no obvious ablation occurred on the surface of the switch electrodes, and it worked normally. When the working coefficient was 68.5%, there were no self-discharge phenomena in a total of 4 000 rounds, and the self-breakdown probability is lower than 2.5×10^-4. The above results show that the switch can meet the needs of high current devices with 300-400 simultaneously working switches.