Proton therapy is a type of advanced radiotherapy that applies a high-energy proton beam to kill target cells by using the special physical properties of protons. In some institutes, instead of proton beams, carbon-ion beams are also utilized due to carbon ions having more ideal physical properties than protons. According to the interaction principle of particles of matter, a heavy ion, such as oxygen ions or heavier ions, could produce a sharper Bragg peak. In other words, heavy ions may show advantages in the dose distribution in comparison to protons or carbon ions. In order to confirm this, we used the Monte Carlo method to simulate the radiotherapy using various heavy ions, and we calculated the dose in the target volume and the normal volumes. The results show that the heavier ion will deposit a higher energy the target volume in the case of the same dose deposition in the normal volumes. In conclusion, in particle radiotherapy, a heavier ion could provide a more ideal physical dose distribution compared to those of protons and carbon.