Membrane fouling is the major limitation to the wide-spread application of membrane bioreactor (MBR). Recently, some additives were used to alter the characteristics of the mixture, and it was found that they could slow down the membrane fouling. This study was to investigate the influence of LaCl₃ and Ce(SO₄)₂ on membrane fouling in MBR. Resistance distribution and specific cake resistance were measured to compare the filterability of LaCl₃ and Ce(SO₄)₂ with blank. The results showed that the two additives could ameliorate the mixture filterability and retard the membrane fouling. At their optimum dosages, the specific cake resistances decreased by 40.93% (LaCl₃) and 49.16% (Ce(SO₄)₂), fouling resistances 96.20% (LaCl₃) and 96.94% (Ce(SO₄)₂) and cake resistances decreased by 79.54% (LaCl₃) and 76.29% (Ce(SO₄)₂) as well. Although the effects of the two additives were similar, LaCl₃ could improve the compression performance of sludge. Besides, the higher optimum dosage of Ce(SO₄)₂ would inhibit the sludge activity in MBR which was not good for the operation of the reactor.