The invention provides a night-soil on-site treatment system. The night-soil on-site treatment system comprises a screw elevator, a solid-liquid separating device, an overlap-spiral type sludge dewatering machine, a chemicals dosing plant and an aerobic fermentation device; wherein the screw elevator, the solid-liquid separating device, the overlap-spiral type sludge dewatering machine and the aerobic fermentation device are connected in sequence, and the chemicals dosing plant and the overlap-spiral type sludge dewatering machine are connected. According to the night-soil on-site treatment system and a treatment method thereof, urban night-soil is separated by a new night-soil pumping mode and working procedures such as solid-liquid separation, screw press dewatering, small dynamic aerobic fermentation, chunks of waste are transported to a refuse transfer station as household refuse, wastewater is transported to a sewage treatment plant via a sewer for treatment, and sludge is subjected to harmless treatment on site, all pollutants are well treated, meanwhile refuse reclamation can be performed to produce an organic fertilizer, the recycling use of resources is realized, and aims of harmlessness, reclamation and reduction of the treatment of the urban night-soil are truly achieved.