The invention provides a ganoderma lucidum culture medium and a preparation method thereof. Compared with the prior art, corn cobs, bean pulp, rice bran and urea are added into an existing ganoderma lucidum culture medium, the carbon nitrogen ratio of the culture medium is controlled, comprehensive nutrients are provided for the growth of ganoderma lucidum, and the growth of the ganoderma lucidum is promoted. Added grape branches and ganoderma lucidum dregs promote the growth of the ganoderma lucidum and synergistically act with magnesium salt and selenium salt, so that the content of calcium, iron, magnesium and selenium in the ganoderma lucidum is improved, and the medicinal value of the ganoderma lucidum is improved; besides, the fruiting rate of the ganoderma lucidum can be improved, the growth of the ganoderma lucidum is promoted, the growth period of the ganoderma lucidum is shortened, and the yield is improved. In the fermentation process, secondary fermentation is adopted, the fermentation temperature and humidity are controlled, the microbial activity is improved, and the growth and fruiting of the ganoderma lucidum are benefited.