In this paper

basic principle of RF-knockout(RFKO) is analyzed for slow beam extraction from the medical proton accelerator

with the amplitude growth mechanism of RFKO method.The amplitude modulation(AM) function model is proposed to obtain a certain uniformity of the beam magnitude.The conditions necessary for a uniform extracted beam

which include RFKO kick angle vs proton numbers of the beam

and kick angle vs the extraction time.Using the WinAGILE code

giving an initial particle momentum distribution

beam distribution is simulated.The relationship among tune deviation

sextupole magnet strength and beam are also simulated.