The invention discloses an intra-cell device to device direct communication method based on user device relay. According to the method, when a first device and a second device in the same cell need to be communicated with each other, if a ProSe server finds the distance between the two devices is too far to meet the distance requirement of device to device communication, the ProSe sends a request message for searching for an available relay device to an eNB (evolved node base) ; after receiving the request message, the eNB searches and feeds a result back to the ProSe server; the ProSe server selects a proper relay device by using the feedback result, and sends a beacon resource request to the eNB; the eNB respectively allocates beacon resources for the first device and the relay device as well as the second device and the relay device, and the relay device and the second device notify the eNB of a communication quality detection result; device to device communication scheduling is performed; after finishing service transmission, the communication devices release the device to device resources. According to the method, the communication is performed in a device to device relay mode, sending power is reduced, user device energy is saved, and the system performance is improved.