Abstract: The ratio of fluctuation amplitudes of wind and solar power was defined, and it was used to improve the correlation coefficients to quantify the complementarity during available periods. Meanwhile, based on the unavailability time of one new energy source and the output amplitude of the other new energy source in the corresponding period, the complementary evaluation indicator of wind and solar energy during the unavailability period was defined. The proposed indicators were used to assess the complementarity of wind and solar energy in Heilongjiang province, and the influence of the installed capacity ratio of wind and solar power on the complementarity was analyzed. Results show that compared with the western region of Heilongjiang, the available and unavailable periods of wind and solar energy in the eastern region show greater complementarity. Over a year, the available periods of wind and solar energy are less complementary in April, while the least complementary periods are available in June, July and August.