More then 70% of the smart meters are with internal load switch, which are purchased by State Grid Corporation of China nowadays. The internal load switch is the most impotent component in the smart meters, and it has important effects on the stability and reliability. This paper analyses the internal load switch and introduces a design of smart meters with the internal load switch driven by motor. This type of meters satisfies all the requirements of State Grid Corporation of China, and can work perfect under the condition of 300mT magnetic field environment.