A polarization-maintaining time-interleaved optical analog-to-digital converter sequentially comprises a mode-locked laser, an optical time division multiplexing frequency multiplication module, a spectrum slicing frequency multiplication module, an optical amplification module, an electro-optic intensity modulation module, a polarization-maintaining connection module, an optical demultiplexing module, a photoelectric converting and processing module and a synchronization module which are connected through polarization-maintaining optical fibers. According to the polarization-maintaining time-interleaved optical analog-to-digital converter, it is guaranteed that the polarization state of an optical sampling pulse sequence in the process of optical time division multiplexing frequency multiplication, spectrum slicing frequency multiplication, optical amplification and transmission does not change on the basis of the polarization-maintaining structure, polarized light emitted by the mode-locked laser always coincides with the polarization axis direction of an electrooptical modulator, and therefore optical pulse amplitude fluctuation caused by polarization dependence is eliminated. A high-stable frequency source of the synchronization module provides same frequency references for the mode-locked laser and an electric analog-to-digital converter, therefore, it is guaranteed that the electric analog-to-digital converter has few shakes on the time interval that a photoelectric detector outputs sampling points of an electronic pulse sequence, and the precision is improved.