This paper introduces a power consumption design of wearable dynamic electrocardiograph (ECG) recorder with the core processor MSP430F5342 to solve the problem that working time of dynamic ECG recorder is not long. By comparing the power consumption of the chip, the MSP430F5 series chipset and the MSP430 MCU clock system are chosen, and the program of the software is used to conduct energy saving control. The low-power design can selectively shut off unused modules, which makes it possible to work in a low-power operating mode most of the time. 3 groups of power test results show that even a small lithium battery of 185 mAh can make its standby time last for 140 d, and the continuous working time can reach 7 d. Because the device uses ultra-small battery capacity, so the recorder has a small size, which makes it suitable to carry and can work for a long time. The low power design of the recorder is successful.