The invention provides an anaerobic decomposition treatment method for organic solid wastes and treatment system thereof. The method includes the following steps that solid-waste treatment objects aredehydrated, dried and decomposed under the heating condition, and carbon powder and decomposition gas are obtained; the decomposition gas is separated refined, and cracked oil, water and combustiblegas are obtained. The treatment system comprises a central control unit, an intermittent decomposition reaction kettle, a decomposition-gas separation refining device and a combustible-gas storage cabinet, wherein the intermittent decomposition reaction kettle, the decomposition-gas separation refining device and the combustible-gas storage cabinet are sequentially communicated, and the central control unit controls the intermittent decomposition reaction kettle, the decomposition-gas separation refining device and the combustible-gas storage cabinet to run. By means of the intermittent treatment method, miniaturization treatment can be achieved, the treatment scheme is simple, few devices are used, the cost is low, the organic solid wastes are not required to be sorted and smashed at thefront stage, are directly put into the intermittent decomposition reaction kettle, and can be decomposed and converted into 'oil', 'gas' and 'carbon', the treatment process is closed in the whole process, and pollution is not charged in the environment.