Multiphoton imaging is extensively used in biomedical research, especially in brain science, providing noninvasive and nondestructive imaging methods for investigating the structure and dynamics of deep biological tissues. However, the absorption and strong scattering characteristics of these biological tissues limit the depth of imaging. Recently, owing to advances in principles and technology, remarkable improvements have been realized in multiphoton imaging with respect to imaging depth in living organisms. Among them, multiphoton imaging obtained by exciting the 1700 nm wavelength band considerably reduces tissue absorption and scattering, achieving the current maximum imaging depth compared with other excitation bands. This article introduces the imaging principles of multiphoton microscopy and utilizes the soliton self-frequency shift effect to construct a femtosecond pulse light source with a 1700 nm band. Furthermore, the application of multiphoton imaging in live mouse brain, skin structure, and hemodynamic imaging is discussed. Finally, the current challenges and future development directions of 1700 nm excitation multiphoton imaging are analyzed and summarized.