A method of generating discovery code for a network entity and a network entity using the same method are provided. In one of the exemplary embodiments, this disclosure is directed to a generating method that is applicable to a network entity and includes at least but not limited to selecting a first substring in a ProSe application code of an announcing UE and a second substring in a ProSe application code of a monitoring UE for a D2D discovery, generating a matching string and a non-matching string according to the first substring and the second substring, and generating a ProSe application mask according to the matching string and the non-matching string.