A semiconductor package with a substrate ID code and its manufacturing method are revealed. A circuit and a solder mask are formed on the bottom surface of a substrate where the solder mask covers most of the circuit and a circuit-free zone of the substrate. A chip is disposed on the top surface of the substrate. A substrate ID code consisting of a plurality of laser marks is inscribed in the solder mask or in a portion of an encapsulant on the bottom surface away from the circuit to show the substrate lot number on the bottom surface. Therefore, quality control and failure tracking and management can easily be implemented by tracking the substrate ID code from the semiconductor package without changing the appearance of the semiconductor package. Furthermore, the substrate ID code can be implemented by the existing laser imprinting machines for semiconductor packaging processes and be formed at the same time of formation of a product code. The complexity of the semiconductor packaging processes is not increased and the circuits of the substrates are not easily damaged.