With the improvement of technology

many new accelerator bunch length measurement methods are in-vented in recent years

such as streak camera

Martin-Puplett interferometer

electro-optic detection

frequency do-main method. Each method has its respective advantages

disadvantages and applied domains. A review on various bunch-length measurement methods is given in this paper. At present many large accelerators in the world universally use streak camera to measure bunch length. For beam bunches of ultrashort duration

optic technology and frequency domain method are adopted

and the resolution of some methods can reach to the order of femtosecond.