Dissolved organic matter (DOM) originated from compost of cattle manure had been extracted and added to Microcystis aeruginosa FACHB905 to study its effects on the physiological and toxin–producing characteristics via the determination of cell growth, pigments content and algal toxins content. The concentration of DOM was evaluated by using dissolved organic carbon (DOC). The final concentrations of DOC designed for cultural medium, marked as CK, T1, T2, T3, T4 and T5, were 0, 15, 30, 60, 90 and 120 mg/L, respectively. The results showed that: 1)Cell density influenced by DOM increased in treatments T1 to T5 at day 2; The maximum growth rate occurred in treatment T4 (5.97×106 cells/mL) at day 2, with a 21.67% increase than that of CK. DOM could increase cell growth in treatments T1 to T3 but inhibit cell density in treatments T4 and T5 at day 4, the maximum growth rate occurred in treatment T2 (9.23×106 cells/mL) with a 15.27% increase than that of CK. DOM could only promote the cell growth in treatments T1 and T2, but inhibit cell density in treatments T3 to T5 at day 6, the maximum growth rate occurred in treatment T1 (13.34×106 cells/mL) with a 10.35% increase than that of CK. 2)Compost source of DOM inhibited the synthesis of algal toxins, the lowest content of Microcystin–LR in cells was occurred in treatment T5 at day 2, with a 53.13% decrease than that of CK. The lowest content of Dha7–Microcystin–LR in cells was occurred in treatment T5 at day 4, with a 78.51% decrease than that of CK. 3)There was no significant effect among DOM treatments on the synthesis of Chl–a or carotenoid in cells.