Initial alignment is one of the key technologies in the inertial navigation system, and the aligned time and alignment accuracy will directly affect the performance of the inertial navigation system.This paper analyzes current research difficulties in initial alignment of the inertial navigation system from the following three aspects:Modeling errors, random errors of the inertial sensor, environmental disturbances and other unpredictable factors.Then, this paper focuses on the current research progress of initial alignment in terms of three types of methods:Traditional two-stage alignment, nonlinear alignment and optimization-based alignment, as well as motion alignment.In future research, the speed, accuracy and applicability of initial alignment of the inertial navigation system will be further improved by taking manipulation factors as disturbances, adding them to the error model, and using a new type of strong tracking filter to deal with underwater nonlinear non-Gaussian noise.