Abstract: During the process of strenthening and retrofitting, a new type prestressed concrete structure with the same tendons, parts of them were existed in the concrete but others were existed as external, is introduced to retrofit the building with a big story hight to more story building. At the first, the general problem in the process of retrofitting such structure was analyzed, then the novel concept was offered and its characteristic was also presented. The methods to calculate the loss of prestressing of the same tendons were given. Then the methods of the ultimate bearing capacity and the limit state of use were also given. At last, an application example was introduced, which proves such methods effective, feasible, and worthwhile wide application.