Abstract: In order to improve the disadvantages that the detection range is close and the probe beam is difficult to be used effectively in the traditional ptychography system, the terahertz ptychography experimental system based on focused Gaussian beam was proposed. Based on the principle of ptychography and using the angular spectrum transmission theory, a focused Gaussian beam was used to replace the diffracted beam generated by the traditional aperture. The feasibility of this replacement was verified through computer simulation experiments, and the corresponding imaging experiments were completed. The numerical simulation results show that it is feasible to carry out the terahertz ptychography using a focused Gaussian beam in the 0.1 THz band, and the simulation and experimental results verify the feasibility of the system. Under the condition of detection distance of 50 mm, the theoretical depth resolution reaches to λ/4, and the experimental system depth resolution is λ/2, which fully demonstrates the effectiveness of this ptychography system.