Presented at the GHRSST XXIII international science team meeting, 27 June-1 July 2022, online and in-person (Barcelona). #GHRSST23 Short abstract The Haiyang-1C (HY-1C) satellite is the first operational ocean color satellite of the Chinese HY-1 series satellites, launched in September 2018. The Chinese Ocean Color and Temperature Scanner (COCTS) on board HY-1C satellite has two thermal infrared channels with the spectrum range of 10.30-11.40 μm and 11.40-12.50 μm for sea surface temperature (SST) observations. The Bayesian cloud detection and optimal estimation (OE) SST retrieval were applied to COCTS data in this study. The Bayesian cloud detection algorithm that has been developed is based on the Bayes’ theorem and used simulation of COCTS observations. The MODerate resolution atmospheric TRANsmission (MODTRAN) model was used for simulation of COCTS brightness temperatures. Global SSTs were retrieved from COCTS by OE from July 2019 to August 2019 and were validated using iQuam buoy SST and Sea and Land Surface Temperature Radiometer (SLSTR) SST. Comparison of COCTS OE SST with buoy SST showed that the COCTS SSTs are cooler than buoy measurements by −0.16 ºC on average, and the standard deviation (SD) of differences was 0.46 ºC. The mean difference of COCTS OE SST with matched skin temperatures from the SLSTR is -0.02 ºC, with a SD of 0.45 ºC. These validation results of COCTS OE SST demonstrated that Bayesian cloud detection and OE SST retrieval algorithm worked well for HY-1C COCTS.