The present invention provides a global positioning system (GPS) and a method for implementing the system. The GPS includes a control unit, a GPS RF processing circuit and a storage unit. The control unit includes a microprocessor and a mask ROM storing reference information. The GPS RF processing circuit is coupled to the control unit for receiving an RF signal, transforming the RF signal into a base-band or an intermediate frequency signal and transmitting the base-band or the intermediate frequency signal to the control unit. The storage unit is coupled to the control unit to temporally store a program code. The microprocessor executes the program code and refers to the reference information to achieve global positioning.