In connection with the situation that it is difficult to measure high-pressure flow in hydraulic system. A new type liquid flowmeter was designed in this paper, shown in Fig.1. The gear flowmeter is the positive displacement flowmeter with good features that the measurement precision is very accurate, and it is not restricted by environmental condition. But the gear flowmeter can't be widely used, just because its flow pulsation is large. After deeply studying the gear flowmeter, the author designed a new planet gear flowmeter. The flowmeter has the characteristics that the displacement is large, and the flow pulsation is small, even less than 1%. It can also be used to measure the flow in high pressure hydraulic system.