Abstract In recent years, wireless or handheld devices have become increasingly widely used, especially in areas such as environmental monitoring and the Internet of Things. However, due to environmental conditions, they cannot rely on the power grid to provide electricity, and energy supply has become a key issue that restricts the deployment and operation of such devices. This article introduces the method and principle of applying a microcontroller control system to a portable emergency DC power supply, and proposes a method for a portable emergency DC power supply with adjustable and stable output. The output voltage can be adjusted in steps of 0.1-15V. This adjustable portable emergency DC power supply not only has the advantages of small volume and low loss of switch mode power supply, but also has the advantages of small output voltage ripple and good output characteristics of linear power supply. It has certain research significance and practical value.