A manufacturing method for molding an image sensor package structure and the image sensor package structure thereof are disclosed. The manufacturing method includes following steps of providing a half-finished image sensor for packaging, arranging a dam on the peripheral of a transparent lid of the half-finished image sensor, positioning the half-finished image sensor within a mold, and injecting a mold compound into the mold cavity of the mold. The dam is arranged on the top surface of the transparent lid and the inner surface of the mold can exactly contact with the top surface of dam so that the mold compound injected into the mold cavity is prevented from overflowing to the transparent lid by the dam. Furthermore, the arrangement of the dam and the mold compound can increase packaged areas and extend blockage to invasive moisture so as to enhance the reliability of the image sensor package structure.