Abstract: Rising temperature causes the degradation of photovoltaic cell power efficiency, and the solar cell temperature is an essential factor to determine temperature reduction coefficients. At present, there are still no sufficient field-recorded data of solar cell temperature in China, and in the design of photovoltaic power plants in different areas, climate background isn't considered enough when the temperature reduction coefficients is determined. Based on observational solar cell temperature, air temperature, ground temperature, inclined and horizontal solar radiation data observed in southern suburb of Beijing, changes of solar cell temperature with time and other meteorological elements are analyzed, and an empirical equation is established for calculating the solar cell temperature. From the point of temporal variation, the solar cell temperature and air temperature or ground temperature are related to a level of consistency, but there are some seasonal differences. For spring and summer (March to August), solar cell temperature and ground temperature are close, which are significantly higher (above 6℃) than air temperature. For autumn and winter (September to December, and January to February) solar cell temperature is significantly higher than that of ground temperature and air temperature. From the point of correlation, comprehensive correlation of solar cell temperature with air temperature and inclined irradiance, and the linear correlation of solar cell temperature with ground temperature are the best, with correlation coefficients exceeding 0.90, and the physical connection are accord with the temperature changes, which are the best choices to calculate solar cell temperature and the temperature reduction coefficient. However, the disadvantages of these equations are that the inclined irradiance or ground temperature data are not easily accessed. The linear correlation of solar cell temperature with air temperature is better, with the correlation coefficient of 0.88, and air temperature is easy to get and the quality is good, which is considered the most practical equation. However, the disadvantage of this equation is that two factors are not the same and the stability of the equation is poor. Comprehensive correlation of solar cell temperature with air temperature and horizontal irradiance is good, with the correlation coefficient being 0.75, which can be used as empirical equation to calculate solar cell temperature at high air temperature conditions. Based on the recorded cell temperature of one year and the weighted calculation, the conclusion is that the annual temperature reduction coefficient of photovoltaic power generation is around 2% in Beijing, and the maximum can reach 13.3%.