Abstract : Insect frass is a novel organic fertilizer, while comparative studies on the improvement effects of insect frass derived from different combinations of agricultural wastes on acidic soils are limited. This study used rice straw as the primary substrate, supplemented with Flammulina velutipes spent mushroom substrate, cow manure, and calcite powder for composting. The composted materials were converted into insect frass by Protaetia brevitarsis larvae. The effects of the decomposed products and insect frass on maize growth, nutrient uptake, soil physicochemical properties, and enzyme activity in acidic soils were investigated. Results indicate that different decomposed products did not significantly affect larval growth or substrate conversion efficiency. The ammonium nitrogen, nitrate nitrogen, and available phosphorus content in insect frass were significantly higher than those in decomposed products. Specifically, the ammonium nitrogen and nitrate nitrogen contents in the cow manure insect frass were significantly higher than those in its decomposed products, increasing by more than two orders of magnitude, while the available phosphorus content increased by 40% compared to its decomposed products. Insect frass derived from substrates amended with mushroom substrate or calcite powder significantly promoted maize growth, particularly the maize dry weight under the mushroom substrate frass treatment (9.47 g) was markedly higher than that under its decomposed products treatment (5.98 g). Compared to decomposed products, frass derived from calcite powder primarily influenced soil physicochemical properties with increased soil pH and ammonium nitrogen content, whereas frass from mushroom substrate and cow manure predominantly enhanced soil enzyme activities, including β-glucosidase and cellulase. Overall, insect frass can further enhance the amelioration effects of agricultural waste composts on acidic soils, while the effectiveness depends on the type of material.