The contents of trace elements (Sr, Mg, Ca) in seawater obtained weekly, 2008 to 2009 from the Sanya Bay, the South Hainan Island were examined using, inductively coupled plasma atomic emission spectrometry (ICP-AES). The results showed that the variation range of seawater Sr/Ca, Mg/Ca ratios were 8.558*10~(-3)~9.227*10~(-3), and 4.924~5.403, respectively, which had an obviously high abnormal deviation compared with the global oceans and the main coral reef. Moreover, during the late spring, early summer and late autumn and early winter, the fluctuation amplitude of the seawater Sr/Ca ratios was relatively bigger than Mg/Ca ratios, and both showed some differences. At the same time, influence of variations of Sr/Ca, Mg/Ca ratios on the coral thermometer calibration, in time and regional space was analyzed. Based on this, the coral Sr/Ca thermometer established in dif-ferent site was re-corrected and it was also compared with the distribution coefficient method. We believe that all kinds of factors including the seawater trace element ratio changes could cause interference to the thermometer calibrations and should be comprehensively considered when reconstructing the SST records by using the Porites corals Sr/Ca, Mg/Ca ratios, which has great significance for further understanding of the climate changes.