Abstract: In order to explore the conditions of high-efficiency electroporation transformation for Escherichia coli DH5a, the key factors in the conditions of electroporation transformation such as the cell growth state, the adding quantity of DNA, the volume of competent cells, electric field intensity, quick freezing and recovery time were optimized, thus to screen the conditions of high-efficiency electroporation transformation for Escherichia coli DH5a. The results showed that: the competent cells of Escherichia coli were prepared when the OD₆₀₀ value of the cell growth state was 0.6. The competent cells were packed in 50 μL per tube, and frozen in ethanol at -80℃. Then, 10 pg pUC 19 plasmid DNA was added, and the cells were transformed by electric shock under the conditions of 20 kv·cm^-1 electric field intensity, 25 μF capacitance and 200 Ω resistance. After the transformation, the cells were cultured for 60 min. The transformation efficiency was above 10¹⁰ cfu·μg^-1 DNA, which could meet the needs of genomic library construction and antibody library screening.