To improve the durability of construction steel， the layered double hydroxide（LDH）crystal nucleus was formed in the steel surface through electrical deposition method. The LDH continued to grow into a dense Mg-Al-NO₃-LDH film through water heat reaction. The effect of the electric sediment voltage on the growth of the LDH film on the surface was analyzed and the mechanism of LDH membrane was discussed. The results show that when the electric precipitation voltage is -1.4 V， LDH nanoparticles are concentrated and stacked together and LDH thin film shape is the densest. A good anti-corrosion protection function on the base of steel is obtained.