Filamentous fungi are widely used in industrial fermentation. Its mycelial morphology is closely combined with objective product yield and fermented liquid viscosity, and it is one of the key factors in the fermentation process control. In this paper, the research progress was reviewed on the mycelia of filamentous fungi in the submerged fermentation,including its morphological characteristics, the analysis and characterization methods, the mechanism of mycelial pellet formation, and the influence of mycelial morphology control in fermentation. Therefore, the author indicated that quantitative description the growth of filamentous fungi was the foundation of precision control on fermentation process.