Abstract: The report introduced species, quantity of microorganism in soilless substrates, effects of microenvironment of soilless substrates on the existence of microorganism and effects of microorganism on crop growth. There were significant differences on species and quantity of microorganism amongst substrates. Species and their activitieswere influenced by environmental factors of in substrates and the main specieswas bacteria and followed by fungi, actinomyces, mildew and so on in the substrates. The microorganisms can help transformation of nutrition in the substrates and enhance stress resistance of p lants, but some fungi and bacterial diseases also occurred in the substrates. The p rospect, direction and p roblem of researches on utilizing microorganism in soilless culture were discussed as well.

Key words: Soilless culture, Substrate, Microorganism