Abstract: Femtosecond lasers not only can generate light pulses shorter than 10fs and obtain a focused pulse peak power of more than 10E21W/cm2 after chirped pulse amplification and compression, but can also be made into a compact, all solid state device with good stability and reliability. They therefore have extremely extensive applications in scientific research. This paper describes the mainproperties of femtosecond lasers and their interaction with transparent materials such as fused silica, optical glasses and PMMA polymers. .The various mechanics of the changes in material properties or structure caused by the nonlinear interactions and their applications in 3-dimensional optical high density huge memories, continuous wave generation and micro-photo-device fabrication are discussed.