Chitin and chitosan were obtained from mealworm larvae (Tenebrio molitor L.) and crab shells. The weight-aver age molecular weight was 764 kDa for Tm-chitosan (Ⅰ), 504 kDa for Tm-chitosan (Ⅱ), and 806 kDa for Cs-chitosan. Oligomer production from Tm-chitosan and Cs-chitosan was confirmed through thin-layer chromatography using a crude enzyme from Pedobacter sp. and chemical acid hydrolysis. The results indicated that in Tm-1 chitosan, GlcN and (GlcN)2 were relatively more prominent than in Cs-1 chitosan, and in Cs-1 chitosan, the reactants of (GlcN)3 to (GlcN)5 were relatively more prominent. High-molecular-weight(HM) and low-molecular-weight LM samples of Tm-chitosan and Cs-chitosan were tested at various concentrations. Antifungal activity was observed at a concentration of 500 ppm, with a mycelial growth inhibition rate exceeding 50% compared to the control, against pathogens Fusarium oxysporum, Alternaria brassicicola, Fusarium solani, and Sclerotinia sclerotiorum.