In order to consider mass lose of frequency part of reaction response analysis, RG1.92(2006)separate nuclear power plant structure, systems, and components(SSCs) into two parts, which are referred to as the "periodic" response and the "rigid" response. Modes of steel frames in the containment vessel distribute in the periodic response region and rigid response region. A response spectrum analysis on a steel frame inside the containment is performed based on Gupta +Missing Mass and Lindley-Yow +ZPA to study the difference of the two methods. The software GTStrudl is used to perform the spectrum analysis based on the two methods above and to find a better way to complete the calculation of Steel frames in containment vessel.