The invention relates to a nano-filtration membrane base material production method based on a wet papermaking technology. The nano-filtration membrane base material production method comprises: S1, preparing disintegrated chemical fiber, and then preparing a slurry, wherein the mass concentration of the slurry is controlled at 0.5-3%; S2, adding a dispersant and an anti-foaming agent before firstslurry rinsing, and feeding into a sand removing device, wherein the dispersant accounts for 1-3% of the mass of the slurry, the anti-foaming agent accounts for 0.01-0.03% of the mass of the slurry,and the sand removing device is divided into at least three sections; S3, feeding into second slurry rinsing; S4, after completing the second slurry rinsing, feeding into a pressure sieve, treating, and adding 0.003-0.006% by mass of a PEO retention aid at the outlet of the pressure sieve; S5, making the slurry prepared in the step S4 flow into a headbox, loading onto a net, and carrying out papermaking; S6, carrying out pressing dewatering; S7, drying; S8, treating by a calender; and S9, winding, carrying out re-winding slitting, and carrying out packaging warehouse. According to the presentinvention, the nano-filtration membrane base material produced by the method has advantages of good paper uniformity, uniform paper quantitation, uniform paper thickness, uniform paper moisture, low banner quantitative deviation and uniform banner moisture, and further has a longitudinal tensile strength of more than 11 kN/m.