Abstract: Based on actual needs, design the serial port circuit of the metering box that integrates high anti modular and uninterrupted meter replacement, integrate breakpoint free bus connection technology, optimize the process of electrical connection points, improve connection firmness, and reduce conduction resistance; complete the design of the measuring box by determining the electrical clearance and creepage distance of the measuring box. The practical results show that the designed method can ensure that the insulation resistance between phases, between phases and the shell, and between phases and the ground inside the measuring box is ≥1000 Ω. At the same time, in a continuous 1 minute 50 Hz, 2500 V AC voltage test, the leakage current of the measuring box meets the requirement of ≤100 mA.