Abstract: Gallium oxide, a wide band gap semiconductor, is a focus material in the semiconductor field at present. Many mature processes have been developed for n-type doping of gallium oxide. However, the conventional doping process has not achieved its p-type doping on bulk crystals, which hinders its application. Proton irradiation transmutation doping is considered to be a more likely p-type doping method than thermal diffusion method and ion implantation method. Proton irradiation transmutation doping is realized by using the transmutation products produced by the nuclear reaction between high-energy protons and target materials. Proton irradiation transmutation doping can put doping atoms at lattice sites. It can also produce more uniform impurity distribution in target materials. What is more, proton irradiation transmutation can produce many elements in gallium oxide crystals. The co-doping effect of many different elements can not be considered as the superposition of single doping effect. Currently, it is considered that two element co-doping has the effect of reducing ionization energy. Therefore, it is hopeful to realize p-type doping of gallium oxide by Coulomb coupling effect of many doping elements imported by proton irradiation transmutation. In this paper, the transmutation doping of gallium oxide irradiated by 100 MeV protons was simulated and analyzed by using the Monte Carlo software FLUKA of nuclear reaction. The simulation conditions were set according to the beam output capacity of the high-current proton cyclotron of China Institute of Atomic Energy. In the analysis, there are 17 kinds of elements and about 80 kinds of nuclides that have significant influence on gallium oxide doping. Over half of nuclides are radionuclides. Simulation calculation was mainly about the activity and transmutation element concentration of gallium oxide after proton irradiation. The results show that the activation activity decreases by about four orders of magnitude after 100 cooling days, and the element concentration of transmutation products tends to be stable. Within the depth range of 1.50 cm of gallium oxide, the specific activity of the target material does not change obviously with the depth. The analysis of element concentrations of transmutation products with different doping types shows that proton irradiation transmutation can generate net p-type doping. The net p-type doping concentration is different at different depths of the target material. It is the largest at the depth of 0.60-0.90 cm, which can reach 4.26×10¹⁴ cm⁻³ per 10¹⁶ cm⁻² proton fluence. Compared with the doping of 40 MeV proton irradiation and fast neutron irradiation, 100 MeV proton irradiation transmutation doping efficiency is higher.