Femtosecond laser is usually utilized to realize the space-selective modification in transparent medium for the induced nonlinear absorption of multi-photon due to its ultrashort pulse duration, high peak density and limited focus area. This review represented the mechanism of femtosecond laser-induced precipitation and controllable crystallization. In addition, recent work on the controllable crystallization of second-order nonlinear optical crystals (i.e., LaBGeO5, LiNbO3 and Ba2TiSi2O4) in oxide glass by femtosecond laser technology and its application in the field of frequency-doubling optical waveguides was also described.