Although polycrystalline materials sintered from nonlinear crystal grains are macroscopically isotropic, the random distribution of grain orientation makes it possible that coherent enhancement of nonlinear polarization occurs when laser interacts with them. Meanwhile, the statistical average value of nonlinear conversion efficiency is proportional to the interaction length. Thus it is called random quasi-phase matching (RQPM). RQPM in polycrystalline materials has a distinct advantage in bandwidth over birefringence phase matching (BPM) and quasi-phase matching (QPM), thus polycrystalline materials are of great significance in frequency conversion for broadband femtosecond lasers. Recently, difference frequency generation (DFG), second harmonic generation (SHG), efficient optical parametric oscillation (OPO), and so on, have been realized based on RQPM in polycrystalline materials, which offers a new low-cost option for supercontinuum and broadband optical frequency combs. This paper summarizes the history and status of the technology and theories of RQPM, discusses the latest achievements on ultra-broadband frequency conversion, introduces the processing and modelling methods of polycrystalline materials, and gives an outlook on the development of RQPM. It is expected that this review can give references to domestic researchers in the fields of ultrafast lasers, nonlinear frequency conversion, etc.