In this article, the in-situ passivation and encapsulation strategy of perovskite quantum dots (PQDs) is proposed using inorganic transparent host (FB, FIREBIRD) and PMMA, respectively. CsPbBr3 are deposited on the surface of FB and FB@ CsPbBr3 composites are obtained. Then FB@CsPbBr3 is coated with PMMA and FB@CsPbBr3/PMMA is prepared. The in-situ passivation and encapsulated CsPbBr3 is very stable in the moisture, heat, and irradiation environment due to the hydrophobic and thermal insulation layers. Meantime, the luminous efficiency of FB@CsPbBr3/PMMA is 70.96%. Furthermore, the white LED (WLED) device is fabricated by combining as-prepared FB@CsPbBr3/PMMA composites, FB@CsBrI2/PMMA composites and a blue LED chip. The Commission Internationale de I’Eclairage (CIE) color coordinates of the fabricated WLED is (0.29, 0.29). A color area of LED device is about 128% of the National Television Standards Committee or 99% of the Rec. 2020 standards. This work provides a novel in-situ passivation and encapsulated strategy through a combination of thin-film packaging and heat-insulating transparent materials which presents a new idea and solution for improving the stability of CsPbBr3.