A hydroponic experiment was conducted to investigate the effects of phosphorus and exogenous auxin on production number of cluster root，physiological characteristics and phosphorus utilization of macadamia seedlings. The results showed that， compared with normal levels of phosphorus supply，low phosphorus treatment significantly increased the number of cluster root in macadamia seedlings by 73.94%，and promoted the exudation of organic acids and enhanced acid phosphatase activity in cluster and non-cluster roots，and the increase in organic acid exudation was mainly dominated by citric and malic acids. The application of Naphthylacetic acid（NAA）also significantly increased the number of cluster root in macadamia seedlings under low and normal phosphorus treatments，and significantly promoted the exudation of organic acids in roots（cluster and non-cluster roots）， and which mainly increased the exudation of citric and malic acids；while the application of Naphthyl o-carbamoylbenzoic acid （NPA）inhibited the generation of cluster root and the exudation of organic acids from roots. In addition，application of NAA also significantly increased the acid phosphatase activity in cluster and non-cluster roots of macadamia seedlings by 13.70% and 30.50% under low phosphorus treatment，while NPA application significantly decreased the acid phosphatase activity by 20.67% and 25.98%，respectively. In this experiment，low phosphorus and auxin application increased the phosphorus uptake of macadamia seedlings by promoting the cluster root formation and changing its physiological characteristics.