For the purpose of comprehensive diagnosis of village sewage systems, an investigation of some village sewage systems was carried out in this study. Seven individual village sewage systems were investigated and its treatment process was one of 4 types; KSBNR, KDHST, YM or LC. Based on this investigation, it can be found that actual inflow of wastewater was much less than design value. Pipeline as well as treatment facility needs fixing up because significant proportion of wastewater was leak from the sewage pipeline. Observed concentration of wastewater was also lower than designed concentration. These low quantity and low quality cause extremely low BOD loading rate as low as 0.2 - 14% of design value. Concentration of mixed liquor microorganisms in the treatment plant was as low as 10-200mg/L for whole types of investigated process and pollutant removal could not be expected. Each of these 4 types of installed process has no nutrient removal mechanisms and can not satisfy the reinforced requirement. KSBNR, KDHST, and YM process could be retrofit to the advanced treatment process for biological nutrient removal system by the resonable modification.