In order to understand the resources utilization of dominant fish species in Kuncheng Lake, the niche breadth and overlap in three dimensions of time, space and trophic were calculated by niche method. According to the value of spatio-temporal and trophic niche breadth, the dominant fish species are divided into wide species, intermediate species and narrow species, and finally the possible reasons for niche breadth and overlap are discussed. The results showed that Coilia nasus, Mongolian redfin (Chanodichthys mongolicus), Toxabramis swinhonis, Pseudobrama simoni, bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), Spotted steed (Hemibarbus maculatus), Paracanthobrama guichenoti, Acheilognathus macropterus and crucian carp (Carassius auratus) were the dominant species. In the time dimension, silver carp has the largest niche breadth and P. simoni has the smallest niche breadth, and 24 pairs of niche overlap are significant, accounting for 53.33% of the total. In the spatial dimension, P. guichenoti is the largest, silver carp is the smallest, and the niche overlap is significant in 36 pairs, accounting for 80% of the total. In the trophic dimension, the largest is crucian carp and the smallest is Spotted steed; there are 8 pairs of niche overlap, accounting for 17.78%. Combined with the three dimensions of time, space and trophic, the niche breadth of crucian carp is the largest, which is the only true wide species, and the smallest is Spotted steed; there are 2 pairs of niche overlap, accounting for 4.44% of the total. The results show that the niche breadth of the dominant species in Kuncheng Lake is mainly affected by seasonal variation, fish ecological habits, proliferation and release. Niche overlap decreases with the increase of dimensions, and finally achieves the goal of coexistence. This study can accumulate basic data for the study of spatio-temporal and trophic niche and biodiversity maintenance mechanism of fishes in shallow lakes in China.