In order to reveal the relationship between temporal and spatial distribution characteristics of phytoplankton functional groups and environmental factors in Qinghai-Tibet Plateau in wetlands, the composition and biomass of phytoplankton functional groups were investigated in the Mitika Wetland in July 2019 (wet season) and October 2019 (dry season). The Spearman correlation analysis, redundancy analysis (RDA) and canonical correspondence analysis (CCA) were used to analyse the temporal and spatial distribution characteristics of phytoplankton functional groups and their relationship with environmental factors in the Mitika Wetland. The results showed that:1) According to the functional group classification method, the phytoplankton in the Mitika Wetland can be divided into 27 functional groups, which were A, B, C, D, E, F, G, H1, J, K, L_M, L_O, M, MP, N, P, S1, S2, T, T_B, T_C, W1, W2, X1, X2, X3, Z. In the time dimension, there were 26 functional groups in the wet season, 23 functional groups in the dry season. In the spatial dimension, there were 24 functional groups in river wetland, 23 functional groups in lake wetland and 12 functional groups in swamp wetland. 2) In the wet season, functional groups A, D, L_M, L_O, MP, N, P, T, T_B and X3 dominated. In the dry season, functional groups A, D, J, L_M, L_O, MP, N, P, T and T_B dominated. Functional groups A and T were the common absolute dominant functional groups in two hydrological periods, and functional group J was the absolute dominant functional group only in dry period. 3) Ecological status index values ranged from 1.80 to 4.86, with an average value of 3.80, indicating that the water quality of the Mitika Wetland was "good". 4) Correlation analysis showed that turbidity, COD_Cr, total phosphorus and nitrate nitrogen were significantly correlated with the biomass of partial dominant functional groups. RDA analysis showed that salinity and total nitrogen were the main environmental factors affecting the biomass of dominant functional groups in the wet season. CCA analysis showed that total nitrogen and nitrate nitrogen were the main environmental factors affecting the biomass of dominant functional groups in the dry season.