Following the promulgation of the standards for arsenic(As)in environment and food people are getting more and more concerned about As pollution and the issue of food safety.It is still controversial over effect of phosphorus(P)supply on uptake and accumulation of As in plant and its mechanism.A hydroponic experiment of tomato(Lycopersicon esculentum,cv. Micro tom)was conducted to verify the effect of P mitigating As stress on plant growth.Addition of 50 mol L^-1 arsenate(AsO₄^3-)significantly decreased the growth of both root and shoot of the tomato plant with P supply ranging from 0.025 to 0.4 mmol L^-1,however,both As concentration in the plant and its inhibitory effect were reduced as P supply rose in level.The roots contained much more As than the shoots.Inhibitory effect of As on P uptake was observed also only at low P supply levels (0.025 and/or 0.05 mmol L^-1 of P).In addition,As had little influence on the expression of the two phosphate transporter genes(LePT1 and LePT2)in tomato.In conclusion,increase in P supply could decrease concentration of As in the plant,thus mitigating the adverse effects of As stress on tomato growth.