NOVELTY - Improving alkaline fermentation sludge acid-producing amount using sodium chloride comprises e.g. taking sequencing batch reactor pilot sludge as fermentation device initial starting sludge, adding sludge in a fermentation reactor (1), starting stirrer (2), starting sodium chloride dosing pump (4.1) when the residual sludge scale mark is reached in reactor, pumping sodium chloride solution, adding sodium hydroxide solution in alkali agent dosing tank (3), pumping sodium chloride solution, stirring, pumping sodium hydroxide into fermentation reactor, detecting e.g. total volatile fatty acid.    USE - The method is useful for improving alkaline fermentation sludge acid-producing amount (claimed).    ADVANTAGE - The method improves the low residual sludge alkaline fermentation condition acid-producing amount, and solves the problem of short stabilizing time in acid production.    DETAILED DESCRIPTION - Improving alkaline fermentation sludge acid-producing amount using sodium chloride, comprises (i) taking sequencing batch reactor (SBR) pilot sludge as fermentation device initial starting sludge, where the sludge concentration is mixed liquor suspended solids (MLSS) is 8000-9000 mg/l, pH is 7-8, soluble chemical oxygen demand (COD) (SCOD) is 30-40 mg/l; after cleaning, the sludge index is: SC0D is 0-5 mg/l, ammonia-nitrogen is 0 mg/l, nitrate-nitrogen is 0 mg/l, when the sludge concentration MLSS is 8000-9000 mg/l, then adding sludge into a fermentation reactor (1), at the same time, starting stirrer (2) and stirring, (ii) starting sodium chloride dosing pump (4.1) when the residual sludge scale mark is reached in reactor, pumping sodium chloride solution, controlling the sodium chloride concentration in the reactor at 0.2-0.5 mol/l, (iii) adding 1-2mol/l sodium hydroxide solution in alkali agent dosing tank (3), pumping sodium chloride solution into the reactor and stirring for 30-50 minutes, starting pump (3.1) and pumping sodium hydroxide into the fermentation reactor, (iv) maintaining the fermentation reactor temperature at 20-30 degrees C, where the mixed liquid pH is 8-10, MLSS is 8000-9000 mg/l, ORP is -100 to -150 mv, and (v) detecting total volatile fatty acids (TVFA), SCOD, ammonia-nitrogen, phosphate ion indicators, operating fermentation reactor for 5-6 days, where TVFA is 1700-2200 mgSC0D/l, SC0D is 3500-4000 mg/l, ammonia-nitrogen is 200-250 mg/l, phosphate ion is 50-60 mg/l, and can be stable for more than 6 days depending on the success of fermentation.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the device for improving alkaline fermentation sludge acid-producing amount.    Fermentation reactor (1)    Stirrer (2)    Alkali agent dosing tank (3)    Starting pump (3.1)    Sodium chloride dosing pump (4.1)