Abstract: In order to obtain a genetically engineered strain of Enterococcus faecium, in this experiment, firstly, the Enterococcus faecium in fresh feces of pigs was isolated and identified by selective medium, and then virulence gene detection, drug susceptibility test, tolerance test and bacteriostatic effect of the isolated strain were tested. The electro-transformation conditions（glycine addition, culture time, washing buffer, plasmid size, plasmid mass concentration, voltage, recovery time, and transformation cup specifications） were optimized for the isolated strain, and the transformed strains were verified by PCR. Finally, the effect of chloramphenicol and glucose in the medium on the growth of transformed strains was analyzed. The results showed that one strain of Enterococcus faecium was isolated from fresh pig feces, which did not contain the virulence genes Asa1, cylA, efaA, esp, gelE and hyl, being sensitive to β-lactam antibiotics（ampicillin, cefothiophene, penicillin G）, tetracycline antibiotics（minocycline）, and chloramphenicol antibiotics（chloramphenicol）, and resistant to aminoglycoside antibiotics（amikacin, kanamycin, gentamicin） and macrolides（erythromycin） and tetracycline antibiotics（tetracycline）. The survival rate of static culture in normal saline at 25 ℃ for 12.5 h did not change significantly（P＜0.05）, and the survival rate was close to 100% while standing for 15 minutes at water temperature below 50 ℃,with a certain tolerance to strong acids and bile salts; it had a certain inhibitory effect on Escherichia coli, Staphylococcus aureus and Salmonella. The isolated strain was made as competent cells for electro-transformation; and the glycine addition amount of 2 g/mL in medium, the culture time of 16 h, and the washing buffer V（300 g PEG1000 mixed with 700 mL ultrapure water）for washing was used to obtain high transformation efficiency during the working process of competent cells. During the electro-transformation process, plasmid mass concentration of 0.878 g/L pAM4010K, voltage of 1 400 V, recovery time of 120 min, and 1 mm transformation cup could obtain high conversion efficiency. PCR proved that the bacterium could successfully import the target plasmid.Whether chloramphenicol was contained in the medium had no significant effect on the growth of transformed strain, and glucose contained had a promoting effect on the growth of transformed strain. The results suggested that the Enterococcus faecium isolated in this test was a potential probiotic strain with the potential to develop into genetically engineered bacteria.