NOVELTY - A two-phase anaerobic digesting system comprises a hydrolyzing and acidizing reaction system, a methane producing reaction system, an aerated methane liquid reflowing system, an external cultivating and activity keeping device for producing acid bacteria, and an external cultivating and activity keeping device for producing methane, where outside of the hydrolyzing and acidizing reaction system is equipped with a methane bacteria cultivating and activity keeping device.    USE - A two-phase anaerobic digesting system for dry clear excrement in pig farm.    ADVANTAGE - The system solves the problems of existing two-phase technique which cannot treat solid pig excrement with high concentration and the efficiency is low; completely solves the problem of traditional anaerobic treatment that the water consumption is high; condenses the methane liquid, and reduces the discharge amount of methane liquid, and greatly decreases the subsequent work of methane project. Organic waste is rapidly degraded and gas is efficiently produced. The comprehensive economic benefit after the system is used can be increased by 20%. The improvement of the efficiency makes the energy of methane project in the pig farm self-sufficient and keeps the methane project in normal operation in winter, thus, realizing the aims of saving water, reducing discharge, protecting environment and producing energy and fertilizer.    DETAILED DESCRIPTION - A two-phase anaerobic digesting system comprises a hydrolyzing and acidizing reaction system, a methane producing reaction system, an aerated methane liquid reflowing system, an external cultivating and activity keeping device for producing acid bacteria, and an external cultivating and activity keeping device for producing methane, where outside of the hydrolyzing and acidizing reaction system is equipped with a methane bacteria cultivating and activity keeping device. The hydrolyzing and acidizing reaction system is connected with the methane producing reaction system, which is connected with the aerated methane liquid reflowing system, which is connected with a hydrolyzing acidizing system. The middle of a hydrolyzing and acidizing reactor (5) with stainless steel shell (17) is a hydrolyzing and acidizing area (1), of which the upper part is equipped with a rotary sprayer (9). The methane producing reaction system comprises a methane producing reactor (6) with a gas outflow pipe (20), a methane-phase water inflow pipe (3) and a water distributing pipe (4). The aerated methane liquid reflowing system is composed of an aerating device (8), an aerating pipe (18), an air pump (13) and a lifting pump II (15).    DESCRIPTION OF DRAWING(S) - The drawing is a block diagram illustrating a two-phase anaerobic digesting system (Drawing includes non-English language text).    Hydrolyzing and acidizing area (1)    Methane-phase water inflow pipe (3)    Water distributing pipe (4)    Hydrolyzing and acidizing reactor (5)    Methane producing reactor (6)    Aerating device (8)    Rotary sprayer (9)    Air pump (13)    Lifting pump II (15)    Stainless steel shell (17)    Aerating pipe (18)    Gas outflow pipe (20)