The invention discloses an oil field water flooding monitoring system based on a PROFIBUS fieldbus, comprising a monitoring host computer, a plurality of master station PLC modules, and a plurality of slave station PLC modules; wherein the monitoring host computer is connected with a printer, each master station PLC module is connected with a first PROFIBUS-DP communication adapter and a touch type liquid crystal display screen, each slave station PLC module is connected with a second PROFIBUS-DP communication adapter; the input end of each slave station PLC module is connected with an operation button, a water knockout trap pressure meter, a pipe pressure meter and a main line flow meter; and the output end of each slave station PLC module is connected with a flow valve, a liquid crystal display screen ad an over-limit alarm. The oil field water flooding monitoring system of the present invention is simple in structure, reasonable in design, convenient in realization, high in system stability, quick in communication speed, high in reliability, good in real-time performance, helpful for improving water flooding efficiency, good in usage effect, and convenient in popularization and usage.