The influence of feed temperature on biofouling of membrane distillation (MD) with respect to the microbial community composition developed on the membrane surface was detailedly investigated in this study. The microbial community profile of MD-membrane biofilm was elucidated during the treatment of Xuanwu Lake water in a flat-sheet bench-scale direct contact membrane distillation (DCMD) system operated under higher feed temperature (60 degrees C) and lower feed temperature (40 degrees C), respectively. The fouling data showed that a more severe flux decline was observed under 60 degrees C, which exhibited a three-phase decline pattern. Comparatively, the normalized flux (NF) of 40 degrees C continuously demonstrated a higher value than that of 60 degrees C, and rather less variations were observed for its decline rate. The combination of SEM-EDS and EEM analysis revealed that more obvious deposition of salt crystals and protein-like substances was observed for the MD membrane operated under 60 degrees C. Phylogenetic analysis using next-generation sequencing of 16S rDNA showed that rather significant shifts of microbial community were observed for the 60 degrees C developed biofilm, while the 40 degrees C formed biofilm bacteria were relatively stable during the MD operation process. Finally, a three-phase model was suggested for the biofilm formation on the MD membrane.