1. A method of encoding group identification in a CDMA trunking system, including the following steps: a trunking group where mobile stations locate being encoded by a preset group identification (GID) encoding method to generate a GID of the trunking group; the GID being a character string consisting of a plurality of decimal digits from 0 to 9 for external processing, and being processed into a binary character string according to a GID type for internal processing; wherein when the GID is used for external processing, it is manifested in a form of a character string consisting of a 16-digit decimal number, the GID comprises: a type identity (TYPE), in the initial place of the GID, one digit, for identifying a GID type; a Mobile Country Code (MCC), three digits, for identifying the country where the MS is located: a Mobile Network Code (MNC), behind the MCC, two digits, for identifying the mobile network; a Mobile Identification Number (MIN), behind the MNC, two digits, as a mobile identification number segment allocated to each country; a Push to Talk (PTT) Home Register (PHR), behind the MIN, three digits, allocated to local network by an operator in a unified way; and a user code, behind the PHR, five digits, as a sole identification number allocated by the PTT home register.