The mycelial morphology during submerged cultivation of Ganoderma ludium using by air-lift fermenter system were analyzed by image processing system and the characterization of mycelial morphology were investigated. In submerged culture using medium with different ammonium phosphate concentrations, the various morphological forms of G. lucidum mycelium were observed. The filamentous forms such as non-branched long filamentous mycelium, non-branched short mycelium, branched long filamentous mycelium, branched short mycelium, entangled mycelium and clump were observed, and also, and also, the pelleted forms such as smooth pellet, rough pellet and hollow rough pellet were observed. The mycelial morphology was changed from the filamentous to the pelleted forms by addition of ammonium phosphate. The fractal dimensions of pelleted and filamentous forms were 1.05 and 1.3, respectively, while the fractal dimension of mixtures of pelleted and filamentous forms was 1.16. Therefore, the fractal dimension was found to be more effective index for the detection of the mycelial morphology and morphological change during batch cultivation. The circularity was also found to be useful for evaluating the surface growth of pelleted mycelium.