In this paper, a series of novel dithioacetal-naphthalenes were designed and synthesized for plant immunity. Their antiviral activities were evaluated against tobacco mosaic virus (TMV) and cucumber mosaic virus (CMV). The results indicated that most compounds exhibited better activity against CMV than against TMV. These dithioacetal derivatives also displayed good bacterial activity against rice bacterial leaf blight. Among them, compound S16 exhibited relatively good anti-CMV, anti-TMV, and antibacterial activity. Structure-activity relationships indicated that introducing the naphthalene moiety enhanced their activities for plant resistance induction. Therefore, the basic motif of compound S16 could be the most promising candidate for further structural optimization to develop a potential activator for plant resistance induction.