Due to high resolution and the ability of reconstructing 3D image of the sample, the terahertz reflection-mode confocal scanning microscopic imaging has great application value. A terahertz reflectionmode confocal scanning microscopic imaging experimental light path is designed. Under the condition of system parameters, the axial response characteristics of the system is calculated and analyzed in the case of two kinds of different wavelengths (118.83 μm and 184.31 μm ). The results of emulation show that the designed experimental device with wavelength of 118.83 μm gains a transverse resolution of 0.23 mm and an axial resolution of about 4.27 mm. When the wavelength is 184.31 μm , the transverse resolution is 0.36 mm and the axial resolution is about 6.63 mm. In comparison with the transverse offset, the axial offset of the detector brings a greater effect.