The invention discloses a cucumber 
seedling substrate. The cucumber 
seedling substrate is prepared from, by weight, 1.5-2.5 parts of 
biogas dregs, 4-6 parts of 
chicken manure, 35-45 parts of biological carbon inoculant, 1.5-2.5 parts of 
straw powder and 1 part of 
perlite. The preparing method comprises the steps of taking components by weight part and mixing evenly the components through a roller. According to the cucumber 
seedling substrate, no grass carbon is adopted at all, therefore, the problems that grass carbon is expensive and is non-renewable in resource are solved, meanwhile the problem that large 
biogas residues pollute environment and an environment 
pollution problem brought by random stacking and arbitrary firing of corn and wheat 
straw are solved, and the cucumber seedling substrate can effectively maintain living and life environment of people, is beneficial to cycle development of 
agricultural economy, and has remarkable economic and 
social benefits. The use of the cucumber seedling substrate can effectively promote the growth of cucumber root systems, meanwhile is beneficial to reducing occurrence of soil-borne diseases, reduces the use of 
chemical agents, and facilitates the production of green vegetables.