Abstract: In order to meet the using demands, one and a half stories were added on the original office building of a police station in Guilin. Treatment methods were used to reinforce and reconstruct the building on the basis of preserving the original structures,such as strengthening foundation,setting foundation outrigger,adding pilaster, increasing section etc. Meanwhile,it is more convenient and faster to set ledger beam in the original slope roof for leveling to ensure a certain distance between beam bottom and the original roof under construction,to avoid the additional load of the beam to the original roof directly,and it is also done the analysis and check of the foundation bearing capacity and settlement. Through a series of effective reinforcement measures,after the transformation all indexes of the building meet the current specification requirements,now it has been used for two years,the using effect is good.