G-protein-coupled receptors (GPCRs) are important protein molecules in the field of cell signaling and are widely found in various organisms. GPCRs play an important role in a variety of physiological processes and are important drug targets for a variety of diseases. Accurate prediction of GPCRs using machine learning is useful for drug design in a variety of related diseases. In this paper, we propose a method for identifying GPCRs based on mixed-feature vectors. We combine three individual features, such as 400D, N-gram and Parallel correlation pseudo amino acid composition (PC-PseAAC), using mixed-feature representation methods, which are evaluated by Random Forest, Naïve Bayes, and J48 for classification purposes. To measure the performance of this classifier, tenfold cross-validation is used. Two dimensionality reduction methods-the max-relevance-max-distance (MRMD) and t-Distributed Stochastic Neighbor Embedding (t-SNE)-are applied to reduce the feature dimension. The 400D and PC-PseAAC feature extraction methods are combined, the random forest is used as the classifier, and the area under the curve (AUC) is up to 0.9413. Therefore, among these methods, the new feature vector obtained by combining the two features shows the best performance, and the mixed feature is better than the single feature. INDEX TERMS G-protein-coupled receptors (GPCRs), J48, mixed-feature methods, naïve bayes, random forest. I. INTRODUCTION G protein-coupled receptors (GPCRs) are seven transmembrane proteins that perform reactions to transduce extracellular signals into cells. Because of their characteristic configuration of seven transmembrane alpha-helical counterclockwise beams [1], GPCRs are one of the largest membrane protein superfamilies, containing more than 800 genes in the human genome [2]. GPCRs are mainly divided into the following six classes [3]: rhodopsin-like receptors, secretin-like receptors, metabo-tropic glutamate receptors, fungal mating pheromone receptors, cyclic AMP (cAMP) receptors, and frizzled receptors. GPCRs bind a variety of ligands, such as small molecule organic compounds, eicosanoids, peptides, and proteins [2]. GPCRs play an important role in many basic physicochemical processes, such as human vision, taste, smell, metabolism, neurotransmission, immune regulation, and cell growth [4-9]. These basic physicochemical processes are carried out by binding of GPCRs with ligand to activate a guanine-binding protein (G protein). At present, most drugs target GPCRs [10, 11], and thus GPCRs are involved in various diseases including depression, diabetes, cancer, and central nervous system diseases are widely targeted in drug development. In the future, accurate prediction of GPCRs is of great significance for drug design for various related diseases. As the data available on GPCRs continues to increase, many methods for predicting GPCRs have been proposed. These methods mainly predict GPCRs from two aspects: one is based on statistical and machine learning algorithms, and the other is based on the extractio...