Mechanical properties of biological cells play an important role in regulating cellular functions. Some micromanipulation methods have been reported in the literature to measure cell mechanics, but they are either high-costly or difficultly-operated. This paper presents our approach to use microrobotic cell injection technology as the test bed to characterize the mechanical properties of biological cells, by virtue of low cost and easy operation. By extending our previous work [41], we develop a mechanical model to interpret the mechanical responses during microinjection and extract the cells properties. Both finite element analysis and microinjection experiments are performed to verify the mechanical model. It is shown that the results obtained from the proposed mechanical model agree well with that obtained from finite element analysis and the experiments. Elastic moduli of zebrafish embryos at different developmental stages are characterized. This demonstrates not only the validity of the proposed model but also the fact that the microrobotic cell injection technology combining with the mechanical model can be used to characterize the mechanical properties of biological cells.