A cell reselection method, adapted to a communication device of a communication system, characterized by the cell reselection method comprising: receiving a first priority information and a Device to Device communication information broadcasted by a network node of the communication system; rearranging the first priority information into a second priority information according to the Device to Device communication information when the communication device is in an operation scenario, wherein the Device to Device communication information is related to whether a plurality of neighbor cells or a plurality of frequencies of the network node support Mode 2 or Mode 1 of Device to Device communication, the Mode 1 represents resource allocation for the communication device by the network node and the Mode 2 represents resource selected by the communication device; wherein at least one neighbor cell in a plurality of neighbor cells of the network node is able to be ranked in the second priority information differently from another neighbor cell in the plurality of neighbor cells, wherein the at least one neighbor cell and the another neighbor cell are operated on the same frequency; characterized in that the step of rearranging the first priority information into the second priority information according to the Device to Device communication information comprises: ranking neighbor cells or frequencies supporting Mode 1 and Mode 2 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies higher than the neighbor cells or the frequencies supporting merely Mode 1 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies; ranking the neighbor cells or the frequencies supporting merely Mode 2 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies higher than the neighbor cells or the frequencies supporting merely Mode 1 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies; and ranking the neighbor cells or the frequencies supporting merely Mode 1 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies higher than the neighbor cells or the frequencies not supporting Device to Device communication of the plurality of neighbor cells or the plurality of frequencies; performing the cell reselection according to the rearranged second priority information. receiving a first priority information and a Device to Device communication information broadcasted by a network node of the communication system; rearranging the first priority information into a second priority information according to the Device to Device communication information when the communication device is in an operation scenario, wherein the Device to Device communication information is related to whether a plurality of neighbor cells or a plurality of frequencies of the network node support Mode 2 or Mode 1 of Device to Device communication, the Mode 1 represents resource allocation for the communication device by the network node and the Mode 2 represents resource selected by the communication device; wherein at least one neighbor cell in a plurality of neighbor cells of the network node is able to be ranked in the second priority information differently from another neighbor cell in the plurality of neighbor cells, wherein the at least one neighbor cell and the another neighbor cell are operated on the same frequency; ranking neighbor cells or frequencies supporting Mode 1 and Mode 2 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies higher than the neighbor cells or the frequencies supporting merely Mode 1 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies; ranking the neighbor cells or the frequencies supporting merely Mode 2 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies higher than the neighbor cells or the frequencies supporting merely Mode 1 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies; and ranking the neighbor cells or the frequencies supporting merely Mode 1 of Device to Device communication of the plurality of neighbor cells or the plurality of frequencies higher than the neighbor cells or the frequencies not supporting Device to Device communication of the plurality of neighbor cells or the plurality of frequencies; performing the cell reselection according to the rearranged second priority information.