Abstract: Double-injection molding methods through which the products do not have any parting lines between the molding materials comprise a mold, which has at least a male mold and a female mold. The male mold comprises at least one core. The female mold comprises at least one cavity and one core. The core of the male mold and the core of the female mold can be combined tightly. The male mold is stationary but the female mold is removable. The molding method of the present invention is to manufacture a product with two different plastic materials, where these two different plastic materials are injected into the mold in a specific order. And these two different plastic materials connect each other directly. After packing and cooling process, these two different plastic materials are shaped in the mold. A product with a smooth profile at the boundary of two materials is thus performed.