The present invention relates to a transmission system with interference avoidance capability, which includes a transmission apparatus and a receiving apparatus. The transmission method thereof receives first data by means of an interference-processing module of the transmission apparatus and adds a plurality of extension data to the first data to produce second data for replacing a plurality of data corresponding to an interfered band in the second data with zero data, and then producing transmission data. The transmission data is converted to a radio-frequency signal by a transmission-processing module and transmitted to the receiving apparatus. Thereby, signal interference can be prevented by avoiding spectrum overlap regions.