The selective LPEE (liquid phase electro-epitaxy) growth of GaAs on GaAs-coated Si substrate prepared by MOCVD has been performed. Several attempts, the use of the insulator melt cap, lowering of the melt height and optimization of the stripe direction, have been tried to increase the lateral growth rate. Very wide (60 μm) lateral overgrowth on the SiO2 mask is obtained by making the stripe window in <010> and equivalent directions and by increasing the lateral current component in the LPEE. The GaAs layer laterally grown on the SiO2 has much less EPD (etch pit density) showing that the defect in the MOCVD-GaAs is blocked by the SiO2. The growth mechanism and the method of increasing the lateral growth rate are discussed.