The variation of irradiance affect the melting rate of the sea ice in the arctic pole, and the research on it is an important component of the global climate change research. The present research was based on the spectrum data collected during the 4th scientific research on the arctic of China in 2010, analyzed the variation of irradiance in the arctic pole during the summer and discussed the reasons for the change. This research shows that many factors lead to the change, among which the weather and the solar elevation angle affect the irradiance directly. The weather factors determine the amount of solar radiation that reached the ground after the absorption and attenuation of the clouds; In high-latitude areas, there is a low solar elevation angle and the attenuation of solar radiation was obvious. Our research shows that the spectrum at shorter wavelength is more sensitive to the changes in altitude of the sun, while the impact of weather on the irradiance increases with wavelength. Moreover, moisture content in the atmosphere also affects the solar radiation reaching the ground and the its impact is in a particular band but not for the entire spectrum range.