The invention provides a method for conveying microorganisms to a stratum. The method is characterized in that microorganisms are carried in a viscous fluid and then go into the stratum by use of a hydraulic fracturing technology, wherein the microorganisms are pretreated so that the microorganisms are in at least one of the following existence forms: a vegetative cell suspension, a starvation-stage cell suspension and a spore suspension. The method realizes carrying the microorganisms deep into the stratum by use of the hydraulic fracturing technology; the microorganisms are appropriately pretreated so that higher conveying efficiency is achieved, and therefore, the microorganisms are enabled to be better in pressure resistance and migration capability, and higher in survival rate. The provided method is advantageous for guaranteeing that related engineering technical operations can be carried out deep into the stratum by using the microorganisms, and especially advantageous for utilizing the microorganisms in the fields of improving the production capacity of a fractured well, improving the oil recovery factor and the like.