NOVELTY - System comprises livestock shed, underground anaerobic reaction bath, acid fermenting bath, submerged mixer and methane fermentation bath. The livestock shed has a porous plate placed to be separated from a bottom surface. The underground anaerobic reaction bath is buried in underground to be chain-installed at the lower portion of livestock shed. The acid fermenting bath receives livestock excretion stored temporarily in the storage tank. The methane fermentation bath receives organic digestion.    USE - As system with underground anaerobic fermentation process of swine slurry.    DETAILED DESCRIPTION - System comprises livestock shed which has a porous plate placed to be separated from a bottom surface to separately collect the livestock excretion excreted by the livestock, underground anaerobic reaction bath which is buried in underground to be chain-installed at the lower portion of livestock shed, receives collected livestock excretion, ferments it with methane, and collects the biogas generated in the methane fermentation through a collecting unit installed at a ceiling space, where the underground anaerobic reaction bath re-supplies a supernatant, which is generated by precipitating the anaerobic digestion remainder fermented with methane, to the livestock shed to reuse it as a washing water of livestock excretion, and the precipitated anaerobic remainder is utilized in a liquefied fertilizer/compost production, underground anaerobic reaction bath comprises a storage tank which receives the livestock excretion generated in the livestock shed to store it temporarily, an acid fermenting bath which receives the livestock excretion stored temporarily in the storage tank and mixes them to hydrolyze them, a methane fermentation bath which receives the organic digestion remainder generated by hydrolyzing in the acid fermenting bath, mixing them to ferment them with methane, and a precipitating bath which receives the anaerobic digestion remainder of methane fermentation bath and precipitate it to allow the supernatant to be supplied to the livestock shed to reuse it as the washing water of livestock excretion and to allow the precipitating anaerobic remainder to be discharged to the outside to utilize it in liquefied fertilizer/compost production, methane fermentation bath and the acid fermenting bath further has submerged mixer which mixes product by the rotation of fan to facilitate the fermentation, submerged mixer is installed slopingly to the upstream to generate the vortex in the methane fermentation bath, and methane fermentation bath further comprises a guide tube extended to the bottom surface of methane fermentation bath to improve the effectiveness of mixing through the submerged mixer by guiding the organic digestion remainder pumped from the acid fermenting bath to the lower portion of methane fermentation bath.