This paper aims to explore whether fly ash, lithium slag, and slag powder (ternary industrial solid wastes) can effectively replace cement as cementitious materials for interlocking large-particle crushed stone bases. A uniform design table U₉(9⁴) was used to design the test scheme for the mixing ratios of ternary industrial solid waste mixtures; the correlation between the mortar strength and the ternary industrial solid waste mixtures was analyzed by Pearson correlation; with the help of the mathematical statistical software SPSS 26.0, mathematical models for the flexural strength and compressive strength of the ternary industrial solid waste mixture mortar specimens were established. The research results show that there is a strong linear negative correlation between fly ash and strength; lithium slag has a weak correlation with strength within a 14-day curing period, and there is a strong linear positive correlation between slag powder and strength. Through the optimization of the mathematical models, the optimal mixing ratio of the three industrial solid waste mixtures is determined as fly ash : lithium slag : slag powder = 40% : 20% : 40%. The tests confirm that the flexural and compressive strengths of the ternary industrial solid waste mixture mortar are significantly improved, which provides strong support for the application of ternary industrial solid waste mixtures in interlocking structures.