The invention discloses a submerged membrane filtration system for removing a suspended solid from phosphating liquid. The submerged membrane filtration system comprises a membrane tank, a membrane module, a backwash tank, a liquid feed pump, a circulating pump, an air blower, a paper filter, a self sucking pump, a backwash pump and a programmable controller, wherein the membrane module is a submerged hollow fibrous membrane module; and in a process of the system, external pressure suction membrane filtration is performed under variable frequency constant current control or variable frequencyconstant pressure, and membrane cleaning is performed according to automatic sequences, wherein the membrane cleaning procedure comprises gas-water backwashing and chemical cleaning. The invention has the advantages that: the submerged membrane filtration system can remove suspension from the phosphating liquid, the content of the suspended solid (SS) in the filtered liquid is low, free acid, total acid and a promoter are not changed, the phosphating effect is good, the operation is simple, the automation degree is high, the service life is long and the energy consumption is low; and the system can be connected with the conventional phosphating liquid treatment system in a phosphating section of a pretreatment production line for on-line use to purify the phosphating liquid in real time, and also can independently treat the waste phosphating liquid for recycle.