In this work, the performance of fusion reactor ITER90H-P with considering D–T and D-3He fuels are examined by writing the dynamics equations on the system reactor. Therefore, we solve these equations analytically in the steady state. In this state we determine the optimum conditions for achieving the maximum fusion gain .In addition, we ignore the impurities because we need to high performance points without impurities. Our calculations in this paper show that we have maximum fusion gain for DT and D-3He fusion reactions in steady state at resonance temperature Kev70 for D-T fusion reaction respectively .Their maximum values of fusion gain are equal to 6.01 for D-T fuel-andthe0.012 for D-3He, respectively. Therefore, currently, using D-3He as a fusion fuel is not recommended.
