This paper presents the design, fabrication and testing of a micro-injector for precision injection of biological cells. Based on the specifications on travel range and injection speed, a single-axis translational motion mechanism is designed by using flexure mechanisms for precision motion guiding of the micro-injector. The mechanism parameters are designed and optimized to cater for the requirements on injection performance. The mechanism performance is verified by conducting finite element analysis simulations. A prototype micro-injector actuated by a piezoelectric stack actuator is developed for experimental testing. A feedback controller is implemented to guarantee the positioning accuracy and response speed. Experiment results reveal the satisfactory performance of the developed micro-injector.