Under hazard load

the important function of engineering structure of small town is lost

the structure is destroyed seriously

even collapse

which causes enormous life and property loss.In order to reduce losses

the index system（including generalized resistance index and generalized load effect index） of small town engineering structure combating a natural disaster

the reliability and the key element were studied from four respects such as

anti-seismic

wind resistance

fire resistance and flood resistance.The computation method of system reliability of the small town engineering structure is simplified according to the correlation of characteristics of the failure modes of small town engineering structure based on resist hazard index.