Abstract: In order to solve the fouling problem of pre-security filters of water treatment equipment inpower plants,the chemical composition of scale sample were analyzed by energy dispersive X-ray spec-troscopy,scanning electron microscopy and transmission electron microscopy. The composition analysisof water source and the compatibility test of chemical agents were carried out. The results showed thatthe main components of the scale sample were aluminum compounds,which existing in the forms ofAlPO4,Al( OH) 3 and Al3( CO3 ) 2. The concentration of residual aluminum ion in the influent was0.34 mg·L-1. Excess aluminum ion reacted with reverse osmosis scale inhibitor and generated whiteinsoluble particulate matters. The turbidity of the solution was positively correlated with the dosage ofscale inhibitor. When adding 27 mL scale inhibitor into 200 mL solution,the turbidity of the solution in-creased up to 4.84 NTU. The residual aluminum flocculants in the influent was incompatible with thescale inhibitor,which would result in fouling. Close-