In this study, we evaluate the dose distributions of 4He and 6He ion beams under the same irradiation settings by using the Monte Carlo method. For the simulations, we defined a water phantom that which includes three normal regions and one target region for measuring the dose deposition in various regions. In addition, we define the 4He and the 6He ion beams with specified parameters. Then, we obtain the distributions of the doses and the tracks of 4He and 6He ion beams and calculate the dose deposited in each region. The calculated results show that in the proximal volume, lateral volume, distal volume, and target volume, the dose depositions of the 4He ion beam are 73.77%, 31.44%, 73.5%, and 98.50% of that of 6He ion beam. In conclusion, we can say from the aspect of physical dose distribution, that the 4He ion beam is more ideal than the 6He ion beam. To more objectively evaluate the therapatic effects of 4He and 6He ion beams, in our need experiment-based study, we will consider the biological effects of 4He and 6He ion beams.