Abstract: A receiver optics designed for KVN(Korean VLBI Network) has been conducting simultaneous millimeter-wave VLBI observations at frequencies of 22 GHz, 43 GHz,86 GHz and 130GHz. The multi-frequency band receiver system has been contributingto a lot of aspects of millimeter wave VLBI observation. This system was constructed using individual receivers in separate dewars. However, this gives in a large optical bench measuring 2600 mm x 2300 mm x 60 mm. Even though the receiver system has performed well by using a unique phase referencing technique to compensate phase fluctuations due to atmosphere, such a large optical bench is inconvenient.Transportation, installation, individual beam alignment for each beam axis is difficult. In order to solve these problems, an integrated quasi-optical circuit using a compact triple band receiver in single dewar is purposed. The recommended frequency bands of the compact triple band receiver are K(18~26 GHz)-band, Q(35~50 GHz)-band, and W(85~115 GHz)-band. A frequency independent quasi-optical circuit for triple band is adopted to obtain constant aperture efficiency as a function of observational frequencies. I will present the design detail of the compact quasi-optical circuit having constant aperture efficiency for wide band and the triple bands receiver optimized forsimultaneous observations.