A reflection-type MEMS multifunction-integrated optical device using the combined in-plane and out-of-plane motion of a dual-slope mirror is proposed. The motion of the mirrors results in the corresponding optical axis offsets in the transmitting and receiving optical signals, which can enable the device with variable optical power splitting, optical switching and variable optical attenuating functions. The optical models for splitting and attenuating are presented, respectively. The electro-mechanical characteristics of the device are also investigated. Measurements of the fabricated devices show that the switching times is less than 9 ms. The excess loss of the device is less than 3 dB and the controllable attenuation range is up to 39 dB, respectively. Moreover, polarization-dependent loss is less than 0.7 dB in the whole attenuation and splitting range.