A method for enabling communication by sensing of a dual-mode dual-standby (DMDS) portable communication apparatus. The DMDS portable communication apparatus includes a processing module, a first light-sensing module, a second light-sensing module, a first communication module and a second communication module. The first light-sensing module, the second light-sensing module, the first communication module and the second communication module are electrically connected with the processing module. The method includes the steps of: sensing by the first light-sensing module so as to transmit a first sensing signal to the processing module; sensing by the second light-sensing module so as to transmit a second sensing signal to the processing module; and correspondingly enabling the first communication module or the second communication module to enter a communication mode by the processing module according to the first sensing signal and/or the second sensing signal.