Objectives To test the impact of provider performance pay for anaemia reduction in rural China. , Design A cluster randomised trial of information, subsidies, and incentives for school principals to reduce anaemia among their students. Enumerators and study participants were not informed of study arm assignment., Setting 72 randomly selected rural primary schools across northwest China., Participants 3553 fourth and fifth grade students aged 9-11 years. All fourth and fifth grade students in sample schools participated in the study., Interventions Sample schools were randomly assigned to a control group, with no intervention, or one of three treatment arms: (a) an information arm, in which principals received information about anaemia; (b) a subsidy arm, in which principals received information and unconditional subsidies; and (c) an incentive arm, in which principals received information, subsidies, and financial incentives for reducing anaemia among students. Twenty seven schools were assigned to the control arm (1816 students at baseline, 1623 at end point), 15 were assigned to the information arm (659 students at baseline, 596 at end point), 15 to the subsidy arm (726 students at baseline, 667 at end point), and 15 to the incentive arm (743 students at baseline, 667 at end point)., Main outcome measures Student haemoglobin concentrations., Results Mean student haemoglobin concentration rose by 1.5 g/L (95% CI – 1.1 to 4.1) in information schools, 0.8 g/L (– 1.8 to 3.3) in subsidy schools, and 2.4 g/L (0 to 4.9) in incentive schools compared with the control group. This increase in haemoglobin corresponded to a reduction in prevalence of anaemia (Hb $<$115 g/L) of 24% in incentive schools. Interactions with pre-existing incentives for principals to achieve good academic performance led to substantially larger gains in the information and incentive arms: when combined with incentives for good academic performance, associated effects on student haemoglobin concentration were 9.8 g/L (4.1 to 15.5) larger in information schools and 8.6 g/L (2.1 to 15.1) larger in incentive schools., Conclusions Financial incentives for health improvement were modestly effective. Understanding interactions with other motives and pre-existing incentives is critical., Trial registration number ISRCTN76158086.