Recently, there is solar radiation matter on cooling loads in office buildings. In the summer, solar radiation has serious effect on cooling loads, therefore if solar radiation are possible to controls, cooling load could be decreased. This study aims on improving energy performance strategy of perimeter zone due to solar radiation in office buildings, and analyze the influence of external shading device that can rely on instrument installation, azimuth and shading length. It was conducted to analyze distinctive features and range of combination of external shading devices due to simulate perimeter model, and eQuest combinations were extracted from the results of simulation model. eQuest simulations were executed to cooling and solar radiation loads of each case. This study analyzed importance, patterns and influence of each case and suggest the guideline that can be used for design reference of office buildings. This study was conducted total 224 cases in the summer solstice which were based on azimuth angles, shading device width and shading installation form. Each case of the perimeter models were predicted to solar gain of window boundary in summer. Simulation tools were used ModelIT, SUNCAST, Apache module of VE(Virtual Environment) to predict energy performance.