The Mars Mineralogical Spectrometer (MMS) is a hyperspectral imager onboard the Mars orbiter of Tianwen-1, China’s first Mars exploration mission. MMS consists of 4 subassemblies: an Optical Sensor Unit (OSU), an Electronics Unit (EU), a Calibration Unit (CU), and a Thermal Control Accessories (TCA). With a 0.5 mrad IFOV and a 416-sample cell array for nadir observation, MMS can map the spectral and spatial information of the Martian surface through push-broom scanning, and it can transmit scientific data by hyperspectral mode or multispectral imaging mode through spatial and spectral combination. MMS can perform multi-sample hyperspectral imaging at full spectral resolution (0.379–1.076 μm with 2.73 nm/band, 1.033–3.425 μm at 7.5 nm/band, both spectral ranges at 2.1 km/pixel at 265 km). For the wavelength region of interest, the multispectral mapping mode provides additional options, a subset of 72 bands that are binned to minimum pixel footprints of 265 m/pixel. The major objective of the MMS is to analyze the compositions and distributions of the minerals on Martian surface, in order to characterize its evolution.