The invention discloses a preparation method of a micro-nano porous impermeable crack-resistance concrete additive, and belongs to the technical field of building water resistance. The preparation method comprises following steps: 1, preparation of a polycarboxylic acid water reducer; 2, raw material mixing; 3, additive mixing; and 4, finished product preparation. According to the preparation method, combined water resistance is replaced by concrete structure type water resistance, water-proof material cost is reduced greatly, multi-layer water-proof construction process is avoided, so that construction time is shortened, construction working efficiency is increased greatly, artificial construction steps are reduced greatly, artificial cost is reduced, and artificial construction imbalancehidden trouble is avoided; a concrete self water-proof system is adopted, so that water resistance lasting period is as long as building service life, in the prior art, maintenance cost is extremelyhigh because of leakage caused by various factors in water proof construction, while almost no daily maintenance is needed in the invented technology.