The invention discloses a modified high-molecular water-absorbent resin for postpartum sanitary napkins as well as a preparation method thereof The modified high-molecular water-absorbent resin comprises the following raw materials: super absorbent resin, diatomite, ferrous sulphate, borneol, vitamin E, olive oil, an extract product of arnebia roots, beta-cyclodextrin, sodium citrate and an extract product of peach leaves. The preparation method comprises the following steps: various raw materials are weighed according to weight parts; a mixture of diatomite, ferrous sulphate, borneol, beta-cyclodextrin and sodium citrate is added into a reaction vessel, the mixture is heated to 120-180 DEG C with stirring, and the temperature is reduced to 50-60 DEG C at a speed of 10-15 DEG C/min in order to obtain a first mixture for standby; the extract product of arnebia roots and the extract product of peach leaves are added in to the first mixture with uniform stirring, plasma treatment is carried out for 3-8 seconds, the super absorbent resin is added with uniformly mixing, and after spray drying, fine powder is obtained. The modified high-molecular water-absorbent resin has the advantages of good imbibition capability and long antimicrobial time; long time usage of the product is helpful for reducing discomfort of private parts, and accelerating healing of lateral incision wounds.