The utility model relates to the field of high molecular weight vegetable protein peptide production, in particular to a reaction system for preparing high molecular weight vegetable protein peptide. The system comprises two or more stages of single-stage enzyme reaction systems; each single-stage enzyme reaction system comprises an enzyme reactor; the discharge openings of the enzyme reactors are connected with the inlets of membrane separating devices through discharge pipes; the non-penetrating liquid outlet of the membrane separating device before the penultimate membrane separating device is connected with the enzyme reactor through a return pipe; the penetrating liquid outlet is connected with the enzyme reactor of the adjacent next single-stage enzyme reactor through a subordinate feeding pipe; pressure pumps are arranged on the discharge pipes, the return pipes and subordinate feeding pipes. The high molecular weight vegetable protein peptide comprises two or more stages of single-stage enzyme reaction systems, and all the single-stage enzyme reaction systems are in series connection; separating membranes with different pore diameters are adopted in the various stages of reaction systems to conduct grading treatment on enzymatic products according to molecular weights; the utilization efficiency of enzyme is improved; the load of the membranes is reduced; the continuous working hours are prolonged.