The commonly used indicators are often too slow to reflect the operating status in time.Confronted with lacking reliable early-warning indices in the single-phase anaerobic digestion for kitchen waste which is easy to decay,lab-scale experiments of start-up and continuous operation process of anaerobic digestion for kitchen waste were carried out in the single-phase anaerobic reactor which is self-designed under mesophilic conditions.Those values which reflect the capacity of acidity-basicity resistance,including the ratio of bicarbonate alkalinity to total alkalinity (BA/TA),absolute testing value of volatile fatty acid (VFA) and the ratio of total concentration for volatile fatty acid to bicarbonate alkalinity (VFA/BA),are determinated to be the early-warning indices for acidification and imbalance of single-phase anaerobic digestion for kitchen waste.It is considered that,when VFA/BA＞0.8,BA/TA＜0.4 and VFA＞3000mg/L,buffering capacity of the system is very poor,and the system might be out of control.Therefore,an immediately steps must be taken.While,when BA/TA≥0.7~0.8 and VFA/BA＜0.4,the alkalinity of system is relatively better and the process can be operated with higher organic volumetric loading,which can raise the biogas-producing efficiency and get economic benefit.