Abstract: The site detection，structural calculation and analysis of a single floor and span double way gradient bent frame structure plant were carried out，then the major problem was discovered that the carrying capacity of the reinforced concrete column dissatisfy the code requirement，and the reliability was confirmed to be class 4，which could not be used normally，so the measures should be taken to strengthen the plant． Through many schemes comparing， steel-encased strengthening technique was adopted to reinforce the concrete column，some defects were repaired，and excellent strengthening effect was got． After disposing，the plants reliability was confirmed to be class l，which can satisfy the normal use requirement，and the plant avoided rebuilding，and abundant social resources were saved．