To achieve the seasonal variation and its ecological impact on the growth rate of blue mussel, the surface (3 m beneath the sea surface) water temperature of the mussel farms around the Gouqi Island was observed for several years. Additionally, the weight and the shell length of blue mussel were also sampled and measured for seven times during a culture cycle. The results showed that the maximum and minimum surface temperature was 29.2℃ and 4.6℃ during the observation, respectively. The amplitude of daily temperature oscillation could be more than 4℃ in the summer, and less than 2℃ in the spring and autumn. Between the weight and the monthly age, a polynomial regression was found as W=0.000 6M⁴+0.006 4M³-0.132 6M²+0.859 9M+0.656 8 (R²=0.999 1). Meanwhile, the polynomial regression between the shell length and the monthly age was found as L=0.000 8M⁴+0.057 7M³-1.099 7M²+7.536 6M+20.044 (R²=0.998 9). The regression relation between the weight growth rate and water temperature is exponential as Rw=0.102 8e^{0.119 5T}(R²=0.741 3). The correlation coefficient is higher when the regression relation between mussel growth rate and water temperature is recalculated by two parts. The exponential relationship is Rw1=0.1488e^0.0683T(R²=0.9360) from October to March of the next year, and Rw2=0.118 8e^{0.128 9T}(R²=0.993 2) from April to August. The regression equation between the shell length growth rate and water temperature is exponential as Rl=0.548 3e^0.1043T(R²=0.952 9). Surface water temperature in the mussel farms around the Gouqi Island varied significantly at the same time between different years. Spring and summer are the important seasons of mussels' growth, continuous relative lower temperature during these two seasons can affect mussel production greatly. The in situ observation of surface water temperature is recommended for the mussel aquaculture,and it could help to adjust culture tactics of blue mussel.