We developed a detailed electroporation method to deliver efficiently siRNA into mouse preimplantation embryos. By introducing Cy3 labeled negative control small interfering RNA (siRNA) into mouse preimplantation embryos, we optimized conditions for the electroporation, including the voltage, pulse duration, pulse number, electroporation buffer and an important step to weaken the zona pellucida. Embryonic survival rate, transfection rate and blastocyst development rate were evaluated under the converted fluorescence microscope, by embryos counting and statistical analysis. The best transfection was achieved in opti-MEM under the conditions of 30 V, 1 ms, 3 pulses, and the duration of digestion in tyrode’s solution was 10 s. In conclusion, the proposed electroporation approach here is a simple and efficient tool to deliver siRNA for RNA interference (RNAi) into mouse preimplantation embryos.