Zebrafish is increasingly used as a model for the pathogenic mechanisms of human disease and drug discovery. Robot-assisted microinjection has attracted much attention due to their great potential in providing high precision and high throughput in biological industry. In this paper, we propose a flexible and integrated robot-assisted microinjection platform, which is able to (1) conduct precise position/velocity control; (2) conduct explicit force control; (3) mimic and repeat manual operations achieved by a skillful technician. The whole system employs modular structure in mechanical design, modeling and control algorithm design, for easy implementation. Experiments performed on zebrafish embryos verify the effectiveness of the proposed robot-assisted microinjection approach.