This paper reviews and summarizes various methods for linewidth measurement, introduces their development process, principles, and the required experimental equipment. According to the difference in principle, the methods for linewidth measurement are divided into two categories based on signal power spectra or phase noises. The limiting factors of linewidth measurement accuracy for these methods are analyzed and the precautions for the operation of these methods are summarized. In addition, the advantages and disadvantages of these methods as well as the corresponding detection ranges are comprehensively listed. According to the performance parameters and experimental conditions for different lasers, suitable linewidth detection methods are recommended. Finally, as for their practical applications, the methods for linewidth measurement of narrow-linewidth tunable lasers (widely used for coherent communications) are analyzed and discussed in detail.