The invention discloses a testing device for the jetting precision of a jet pump. The testing device comprises a shell, an expansion body separator and a real-time reader. Scales are arranged on the side wall of the shell, an inner pipe stretching into the shell is arranged on the side wall of the bottom end of the shell, a liquid inlet pipe used for being connected with a jetting pipe of the jet pump is arranged on the outer side of the inner pipe, and a gas-liquid outlet and a liquid backflow port are formed in the top end of the shell. The expansion body separator is arranged at the top end of the shell and comprises a spherical outer shell and a spherical inner shell. A discharging port is formed in the outer wall of the spherical outer shell, and the spherical outer shell communicates with the liquid backflow port. The spherical inner shell is fixedly arranged in the spherical outer shell, a plurality of radial spraying pipes are arranged on the circumferential wall of the spherical inner shell and are aligned with the inner wall of the spherical outer shell, and the gas-liquid outlet penetrates the spherical outer shell and communicates with the spherical inner shell. The real-time reader is used for reading the volume variation of liquid in the shell in real time through a differential pressure sensor. The testing device can accurately detect the jetting precision under different jetting flow degrees.