The 2 μm wavelength band, which is the closest to the O and C communication band in the mid-infrared band, has gradually attracted widespread attention. A Mach-Zehnder modulator in the wavelength of 2 μm was optimally designed and simulated. According to the distribution characteristics of the optical mode field in the wavelength of 2 μm, an SOI substrate with the top silicon thickness of 340 nm was selected. Combined with the process of the etching depth of 240 nm, the optimal rib waveguide width was 600 nm and the thickness of the slab layer was 100 nm. By optimizing the doping concentration and the positions of the doping regions, an optimal overall performance of the modulator was obtained. The modulator operated with the static extinction ratio of 23.8 dB, the optical loss of 5.34 dB/cm, the modulation efficiency of 2.86 V·cm and the 3 dB EO bandwidth of 27.1 GHz at the reverse bias of 4 V. Besides, compared with the device with the top silicon thickness of 220 nm, the overall performance of the modulator was more superior. The research content provides a basis of the device tape-out, and also provides a new idea for the design of the modulator required for the 2 μm band optical transceiver integrated module.