In order to meet the requirement of increasing transmission rate, the future communication technology will naturally develop to a higher carrier frequency, and terahertz communication technology becomes a possibility. Aiming at the I/Q imbalance problem in terahertz communication system under the background of large bandwidth, an I/Q imbalance damage model is constructed under terahertz zero-intermediate frequency architecture. The algorithm derivation and compensation architecture design are completed in corresponding narrowband and broadband scenarios, and the algorithm performance is improved by improving the cost function for broadband scenarios. The simulation results show that the Mean-Square Error (MSE) of the proposed algorithm is improved by 15 dB compared with that of the statistical algorithm. In the experiment of 220 GHz zero intermediate frequency communication system, the MSE of narrowband algorithm proposed in this paper is improved by 7 dB, and that of the broadband algorithm is improved by 1 dB.