Belonging to the technical field of carbon nanomaterial preparation, the invention relates to a microporous-mesoporous carbon, a preparation method and application thereof. The preparation method includes: putting citrate in a tubular muffle furnace, providing nitrogen protection, conducting high temperature activation and carbonization, and then performing cooling to room temperature; conductingpickling, drying and grinding on the obtained substance to obtain mesoporous carbon; mixing the obtained mesoporous carbon with an activator evenly, conducting high temperature activation and carbonization, and then performing cooling to room temperature; and carrying out pickling, drying and grinding on the obtained substance to obtain microporous-mesoporous carbon. The microporous-mesoporous carbon prepared by the method provided by the invention has large effective activation area and good activation effect. By fixing the prepared microporous-mesoporous carbon to a stainless steel wire surface by means of physical adhesion, a novel, cheap and efficient solid phase microextraction probe can be prepared, and can be used for detecting volatile organic pollutants in a water environment.