G-protein-coupled receptors （GPCRs） mediate many important physiological functions and are considered as one of the most success- ful therapeutic targets for a broad spectrum of diseases. The design and implementation of high-throughput GPCR assays that allow the cost-effective screening of large compound libraries to identify novel drug candidates are critical in early drug discovery. Early functional GPCR assays depend primarily on the measurement of G-protein-mediated 2nd messenger generation. Taking advantage of the continuously deepening understanding of GPCR signal transduction, many G-protein-independent pathways are utilized to detect the activity of GPCRs, and may provide additional information on functiona~ selectivity of candidate compounds. With the combination of automated imaging systems and label-free detection systems, such assays are now suitable for high-throughput screening （HTS）. In this review, we summarize the most widely used GPCR assays and recent advances in HTS technologies for GPCR drug discovery.