The embodiments of the invention provide a proton source which comprises a first shell and a waveguide tube. A discharging cavity is formed in the first shell and the waveguide tube is used for importing microwaves into the discharging cavity, wherein the frequency of microwaves imported by the waveguide tube is in the range of 14-18GHz. According to the invention, the working microwave frequencyis relatively high, so that the sizes of the waveguide tube and the discharging cavity are small and the proton source is accordingly small and compact.