  The proton synchrotron radiation is considered as the origin of high-energy
emission of blazars at times. However, extreme physical parameters are often
required. In this work, we propose an analytical method to study the parameter
space when applying the proton synchrotron radiation to fit the keV, GeV, and
very-high-energy emission of blazar jets. We find that proton synchrotron
radiation can fit the high-energy hump when it peaks beyond tens GeV without
violating basic observations and theories. For the high-energy hump peaked
around GeV band, extreme parameters, such as a super-Eddington jet power and a
very strong magnetic field, are required. For the high-energy hump peaked
around keV band, if an acceptable parameter space can be found depends on the
object's keV luminosity.
