Modified technology by grafting double silicon film to SrAl₂O₄：Eu²⁺，Dy³⁺ luminescent powder was used to protect luminescent powder. Sodium silicate was used as thefirst layer of inorganic silicon coating by chemical precipitation method，KH570 was adopted to prepare the second layer of an organosilicon film by sol-gel method，and then an acrylic filmwas grafted to powder. The double-layer silicon coating was used to enhance the moistureresistance and organic compatibility of luminescent powder. Then，the performance test was carried out，and the properties of the luminescent powder were evaluated comprehensivelythrough moisture resistance，fluorescence properties，and thermal stability. The tests showedthat the complete coating of luminescent powder could be achieved by grafting modification technology of double-layer silicon. The pH growth rate of the luminescent powder aqueousdispersion was reduced by 64. 9%，indicating that the moisture resistance had been significantly improved. As the best modification formula，80% sodium silicate and 10% silane coupling agent KH570 could achieve the best improvement effect. The fluorescence of modified luminescent powder could reach 194. 4 mcd/m² and 24. 3 mcd/m² at 10 min and 60 min. The afterglow time was 12. 8 h. The thermal stability showed good results. The research had potential application value for realizing the durable luminescence of road markings and improving the visibility in rainy night environments.