In order to solve the large-sized and low-precision problems of traditional injection pump using stepper motor system, a lead linear ultrasonic motor is utilized as the driving element of this injection system, and the flow velocity can be controlled by adjusting the voltage and duty factor of driving signal. The size of the motor is 4mm×4 mm×15 mm which satisfies portable requirement and overcomes the large-sized problem. In flow velocity experiments, the voltage and duty factor of driving signal can be used to accurately control the flow speed. Without any speed reducer, the maximum of flow velocity reaches 61.87μL/s at 300Vp-p and 100% duty factor, and the minimum of flow velocity is 0.01μL/s at 200Vp-p and 1% duty factor. The injection system can stably work at the minimum flow velocity, and its precision is better than traditional injection pump whose minimum is 0.028μL/s. Therefore, this control method of injection system with ultrasonic motor can improve the accuracy up to 0.01μL/s with a small size, and it also has a good output performance.