The flow rate of coolant and the particle beam current are important when high beam current irradiations are intended for production of radionuclides. The beam current on natCu target to produce 63Zn via the natCu(p,n)63Zn reaction was investigated and the beam current was obtained more than 350 μA that is the maximum allowed beam current used for producing medical radioisotopes in Nuclear Science and Technology Research Institute of Iran. In addition, the temperature distribution on the target under the different cooling water flow rates has been simulated based on finite element analysis program. The results show that the cooling water flow rate can be brought down to 1.5 L/min without the risk of melting of target material and boiling water. •The beam current on natCu target to produce 63Zn via the natCu(p,n)63Zn reaction has been numerically analyzed.•The optimum thickness of natCu target is calculated from the nuclear cross-section data and SRIM-2013 calculation.•The highest proton current to produce 63Zn radionuclide was estimated.•To determine the optimal design of the target, the distribution of temperature was calculated using the COMSOL program.