In this project, feasibility of direct production of praseodymium-140 radioisotope by direct method using 140Ce(p,n)140Pr reaction excitation function obtained from the calculation code TALYS-1.8 has been investigated. On the other hand, due to the short half-life 3.39m, this radioisotope can be produced in small portable cyclotron to medical centers. Using the excitation function, the optimal energy range for the proton projectile to achieve the maximum product cross-section 140Pr and the minimum isotopic and non-isotopic contamination caused by other decay channels during the reaction, it is determined. Finally, the theoretical production yield is compared with the simulated production yield, which are directly and indirectly derived from the MCNPX code.