The invention discloses an admixture for improving and maintaining the construction performance of pervious concrete and a preparation method of the admixture. The admixture is mainly prepared from the following main raw materials: a water reducing agent, cellulose ether, a guar gum-xanthan gum copolymer, polyacrylamide, an air entraining agent, dispersible latex powder, a retarder and a wetting agent. The pervious concrete admixture prepared by the preparation method disclosed by the invention has the advantages that the wrapping property, uniformity and water-retaining property of pervious concrete slurry can be remarkably improved, the evaporation rate of surface water of the concrete is slowed down, the slurry is enabled to be uniformly distributed on the surface of aggregate, arbitrarily regulation and control of the construction operable time within 3 to 5 hours of the pervious concrete can be realized, the performance of the pervious concrete is kept stable within a relatively-long operation time and the requirements of premixed long distance transportation can be met; in addition, the preparation method disclosed by the invention has the characteristics of simple productiontechnology, low price, high application cost performance, no pollution and the like.