The dumping site for copper mining tailings at Yangshanchong at Tongling city (Anhui Province) has been deserted for 20-years. The area is characterized by extremely high concentrations of heavy metals, poverty of nutrients, easy acidification and severe desertification. Biological soil crusts (BSCs), extensively existing on tailings is a major early stage of the ecological succession of the tailing ecosystem. The method of in situ acetylene reduction was applied to explore characteristics of biological nitrogen-fixation of algae, algae-moss and moss crusts on tailings. It was found that biological crusts significantly increased total nitrogen and lower Cu content in the tailings, and the nitrogen-fixing capability of the crusts varied sharply from type to type. Among the three types, the algae-moss type of crust was the highest in N₂ fixation rates, ranging between 1.32~8.78 kg hm^-2 a^-1, and followed by the algae type and the moss type, ranging between 4.36~30.39 kg hm^-2 a^-1 and between 0~16.34 kg hm^-2 a^-1, respectively, and followed a decreasing order of algae-moss, moss, and algae BSCs. N₂ fixation capacity of the BSCs varied with the season, too showing a decrease order of summer, spring, fall and winter. Besides, a negative line relationship was observed of the capacity with soil bulk density, NO₃^--N, and total Cu concentration and a positive one with pH, NH₄⁺-N, and water soluble organic carbon. On the whole, BSCs significantly enhanced total nitrogen content, and decrease total Cu concentration in tailings. The anomalous wet conditions experienced during the year of the study may have increased the temporal availability of soil mineral N and decreased N fixation rates. However, the presence of N fixation activity in all crusts analyzed their ability to survive at high Cu concentration, which may contribute to ecosystem resilience and recovery in areas under severe heavy metal stress.