The invention relates to a method of manufacturing an optical fiber perfrom mandrel by PCVD deposition. The method is characterized in that needed sectional area distribution, refractive index distribution and flows of controlled reaction gas at different times actually required by a refractive index profile according to the sectional area distribution, the refractive index distribution and the refractive index profile of a previous deposited perform mandrel and flows of controlled reaction gas at different times of the previous deposited perform; accurate flow control is performed on one or more controlled reaction gas by means of a rapid flow control module and a flow measuring module in different radial and axial positions of mandrel deposition, so that the refractive index, the refractive index profile and in-tube deposition of sectional area of a core layer are precisely controlled. According to the method provided by the invention, the parameters of the optical fiber perform by means of microwave plasma chemical vapor deposition can be improved, the uniformity of distribution of depositing liner parameters is improved, the effective length of the mandrel is increased, and the manufacturing cost is lowered.