Abstract: Based on the analysis of the seismic performance of 16 partially prestressed concrete (PPC) frame structures designed according to China current codes, the quantitative index of PPC frame performance levels and the reliability of a design displacement in Direct Displacement-Based Design (DDBD) had been analyzed. After three performance levels of basic integrity, life safety and collapse prevention defined, crack width, bearing capacity had been suggested as a quantitative reference index and the corresponding interstory drift ratio as a final quantitative index. At the same time, taking the interstory drift ratio corresponding to a quantitative index as resistances and corresponding to expected earthquakes as effects, a simplified method had been put forward, in which reliability can be taken into account in DDBD and associated to the reliability level of current codes. In this method, the error arose from the coefficient of variation can be avoid greatly and different requirements can be satisfied under an identical performance level.