A firedamp preparation method with wasted vegetable as the raw material is provided, which belongs to the energy technical field. The invention the following steps that: at first pretreatment is made on the wasted vegetable as the raw material to adjust the carbon / hydrogen ratio to be 20:1-30:1, then inoculation with the inoculumis carried out, followed by mixing, to obtain the fermented raw material, then water and carbon powder are added for fermentation, with the original pH of fermentation liquid adjusted to be 6.5-7.5, then put into a sealed fermentation device, and immersed in a thermostatic water bath, to carry out the perfect mixing liner wet aerogenous fermentation, to produce the firedamp after 1-2 days, fermentation is carried out for 20-60 days, and the gas is collected with drainage method. The invention accomplishes sufficiently the utilization of wasted vegetable for resourcesiation, reduction and innocuity, and transforms the vegetable harming the environment into biological resources, which produces firedamp as the clean burnable energy and excellent organic fertilizer through anaerobic fermentation.