A method for molding a two-piece blow molded hollow tank by using auxiliary male molds includes the following steps: 1) blanking two parisons; 2) closing mold halves of a mold and a pre-molding template; 3) pre-stretching the molten parisons by using auxiliary male molds in the pre-molding template; 4) performing internal high-pressure blow molding, and pre-molding two housing portions; 5) opening the mold, and withdrawing the pre-molding template; 6) moving in a component built-in mechanism to perform built-in component connection; 7) moving out the component built-in mechanism; 8) closing the mold for the second time and finally blow molding a hollow tank; and 9) opening the mold and taking out the product.