Laser beam combining is, at present, a worldwide hot spot of research in the field of laser technology. It is an effective approach to scale laser output power and brightness greatly by combining some individual laser beams into one beam for output. The incoherent beam combining of fiber laser arrays features of simple configuration and is easy to control. The research on it has been developed rapidly in recent years and the combined output power has already reached the order of kilowatt level. Recent progress of incoherent beam combining of fiber laser arrays is reviewed. The fundamental principles of various types of combining scheme, including the incoherent beam combining with outer cavity, the incoherent beam combining based on PTR Bragg grating and the incoherent beam combining using adaptive optics, are presented. From both aspects of scheme's configuration and practical application, the advantages and disadvantages of these schemes are analyzed and compared. Since single-mode laser is less affected by atmospheric conditions and propagates more far than multi-mode laser, the incoherent beam combining scheme based on adaptive optics is more suited to be used as the light source of directed energy system. Finally, some key problems blocking the combined output power scaling to the order of 100kW level are pointed out, which involve increasing the output power of individual fiber laser, settling the distortion of combining element under high power and designing and optimizing the combining scheme of more beams.