In this paper, a cheap silica source solution was obtained from waste glass for the preparation of silica aerogel (SA). Subsequently, SA was loaded in porous expanded perlite particles for effective utilization. The results show that the dissolution time of the glass powder in the hot alkali solution must be greater than 4 h, so that the formed silica source solution can be made into structurally desirable SA, whose pore structure and thermal conductivity are better than those of water glass. 10 min of processing time at a relative vacuum pressure of -0.08 MPa can produce expanded perlite loaded with silica aerogel (EPA) with better performance. The same volume of sand is substituted using EPA for mortar preparation. The thermal conductivity of the mortar decreased as the substitution rate increased.