This study investigated the effects of Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus velezensis on the growth of cucumber seedlings using kitchen waste compost substrate. The results indicated that B. subtilis and B. velezensis significantly improved chlorophyll content, leaf area, and biomass of cucumber seedlings. However, these Bacillus species did not enhance root growth. B. velezensis exhibited the highest growth-promoting effect based on the strength index and affiliation function method. All three Bacillus species significantly increased the electrical conductivity of the substrate but had no significant effect on the substrate’s pH. Additionally, they did not significantly reduce the Na+ and Cl- content of the substrate. The Bacillus treatments significantly elevated the content of alkaline dissolved nitrogen and fast-acting potassium compared to the control. However, B. velezensis resulted in significantly lower effective phosphorus content than the other treatments. Further research is recommended to address the residual salt ions from kitchen waste compost in substrates or soil to ensure the safe and effective use of kitchen waste compost in agricultural production.