In an attempt to search for natural product-based antifungal agents, twenty novel dehydroabietic acid-based B ring-fused-thiazole-amide compounds (Ⅵa~t) were designed and synthesized by using dehydroabietic acid as a starting material. The synthetic conditions were investigated preliminarily, and the target products were characterized by FTIR, 1HNMR, 13CNMR, and ESI-MS. The antifungal activity was also evaluated against the following 5 plant pathogens: Fusarium oxysporum f. cucumerinum, Cercospora arachidicola, Physalospora piricola, Alternaria solani, and Gibberella zeae. The preliminary bioassay showed that, at the concentration of 50 mg/L, the target product dehydroabietic acid-based B ring-fused-thiazole-benzamide (Ⅵj) and the intermediate dehydroabietic acid-based B ring-fused-thiazole-amine (Ⅴ) had inhibition rates of 90.0% and 92.4% against Physalospora piricola(A-class activity level), respectively.