A systematic analysis and optimum design have been reported for the integration of the Si1-xGex optical switch and the Si1-xGex/Si infrared detector at λ=1.55 μm. The optimizing design results are:(1) For the Si1-xGex optical switch,Ge content x=0.05. Waveguide height,width and etched depth are 3, 8.5 and 2.6 μm, respectively, branch angles are 5～6°, and the bias voltage of pn+ junction is 0.97 V.(2) For the Si1-xGex/Si infrared detector, Ge content x=0.5. Total thickness of the detector is 550 nm, shich consists of 23 periods alternate 6 nm Si0.5Ge0.5 +17 nm Si. The length of the detector is about 1.5～2 mm. The results show that the internal quantum effciency of the detector of this structure can be as high as 80%.