A two-dimensional piston dynamic flowmeter was proposed, which utilized the two-dimensional piston with two degrees of freedom as a measuring unit. The two dimensional piston simultaneously performed both reciprocating and rotating motions. Therefore, the flowmeter took into account the high dynamic characteristics of the no-loaded dynamic cylinder to measure the unsteady flow, and the ability of the rotor flowmeter to continuously measure the flow rate. The mechanical structure and working principle of the flowmeter were explained, and the corresponding mathematical model was obtained by establishing the dynamic equation and flow continuity equation to study the dynamic characteristics of the flowmeter. After that, a prototype was designed and manufactured. A dynamic performance test bench was built for experimental research. The results of experiments showed that the two-dimensional piston dynamic flowmeter had better dynamic characteristics. When the oscillation frequency of the measured sinusoidal flow signal reached 5Hz, the frequency of the flow measured by the two-dimensional piston flowmeter was almost the same as that measured by the no-load dynamic cylinder, and the phase difference between these two signals was close to zero. However, the amplitude attenuation of the output signal of the flowmeter was more serious, which was caused by the presence of air in the flowmeter.