Abstract: One main reason of low efficiency producing transgenic animal by microinjection is digestion of foreign DNA by nucleases in nuclear. Recombinase RecA can protect DNA from digestion by phosphodiesterases or nucleases. A recombinase RecA-mediated mouse transgenesis method was developed. Further, we discussed the effect of recombinase RecA on production efficiency of transgenic mouse by microinjection. 41 F0 mice were obtained by microinjecting complexes of single strand DNA and RecA protein. Using single strand DNA and double strand DNA for microinjection, 28 and 32 F0 mice were obtained, respectively. All F0 mice were determined to be transgenic by PCR and Southern blot. The result showed that 14.6%（6/41） of F0 mice produced by pronuclear microinjection of RecA coated ssDNA was transgenic. The production efficiency of transgenic mouse was 6.2% when dsDNA was used. There was no transgenic when ssDNA was used.