The utility model discloses a turbine speed measuring system based on a diffusion reflection optical fiber sensor, which comprises a turbine rotating speed detection circuit module, a microprocessor module connected with the turbine rotating speed detection circuit module, and a power management circuit module, wherein the turbine rotating speed detection circuit module is composed of a diffusion reflection optical fiber sensor, a pre-amplification circuit module and a photoelectric coupling circuit module which are sequentially connected; the diffusion reflection optical fiber sensor is installed on a turbine shaft; an output end of the microprocessor module is connected to a first digital tube display circuit module, a second digital tube display circuit module and a logic level conversion circuit module; an output end of the logic level conversion circuit module is sequentially connected to a D/A conversion circuit module and a V/I conversion circuit module which is used for converting voltage signals into current signals and transmitting the current signals to a turbine DCS (distributed control system). The turbine speed measuring system disclosed by the utility model is reasonable in design, convenient to install and use, high in detection precision, high in work reliability, long in service life, good in expansibility, and convenient for popularization.