Abstract: Residue-residue interactions between individual subunits of protein complexes are critical for predicting complex structures and can serve as distance constraints to guide complex structure modeling. Some recent studies have made some progress in predicting protein inter-chain contact maps based on multiple sequence alignments and deep learning models. Here we develop a new model based on graph attention network and triangular multiplication update to predict interchain contact maps for homologous protein complexes, named PGT (P is Protein, G is Graph attention network and T is Triangular multiplication update). Different from other methods which need to perform multiple sequence alignment processes and extract complicated manual features, PGT extracts embeddings of residues through protein language model. Besides, we introduce structural information through graph attention network to learn the spatial information of subunits from complex structure and utilize the triangular multiplication module to capture triangular constraints between residues. To demonstrate the effectiveness of our method, we compare PGT with previous works such as DeepHomo, DRCon and Glinter on two independent test sets. The results show that PGT substantially outperforms these methods. Furthermore, we also perform two ablation experiments to demonstrate the necessity of introducing graph attention network and triangular multiplication update. In all, our framework presents new modules to accurately predict inter-chain contact maps in homologous protein complexes and it's also useful to analyze interactions in other type of protein complexes.