Abstract: Cucumber was selected as the test material, the decomposed cow manure and spent mushroom substrate were used as the main substrate raw materials.A cucumber seedling experiment was conducted by adding different volumes of peat and vermiculite as the substrate composite.The physical and chemical properties of different ratios of substrates and their effects on cucumber seedling cultivation were studied, in order to screen suitable substrate formulas for cucumber seedling cultivation and provide reference for the substrate utilization of decomposed cow manure, spent mushroom substrate and other waste materials.The results showed that compared with the control, the substrate with a ratio of peat vermiculite∶decomposed cow manure∶spent mushroom substrate=70∶10∶20 had the appropriate physical and chemical properties, with a seedling emergence rate of 98.67% and the highest uniformity.It could significantly improve the stem thickness and leaf area of cucumber seedlings, with the highest aboveground and underground dry weights of 0.19 g and 0.02 g, respectively.The seedling comprehensive evaluation index was the highest, reaching 0.914 6,indicating the best comprehensive performance.It was recommended to use a mixture of peat vermiculite∶decomposed cow manure∶spent mushroom substrate=70∶10∶20 as the substrate for cucumber seedling cultivation.