Metalaxyl is frequently used to protect a variety of crops from fungal diseases. This study aims to establish a method for the determination of metalaxyl in Chinese bayberry, fresh Dendrobium officinale (D. officinale), and dried D. officinale by gas chromatography-tandem mass spectrometry (GC-MS/MS) and further assess dietary risk. The samples were extracted with acetonitrile and purified by the dispersed solid phase extraction method. Chinese bayberry, fresh D. officinale, and dried D. officinale samples were collected from Hangzhou and Zhangzhou in 2021 to clarify metalaxyl residue levels. The metalaxyl was quantitated by the external standard method. In the range of 0.001–0.1 mg L⁻¹, there was good linearity under the optimal conditions. The recoveries ranged from 83.90% to 110.47%, with relative standard deviations ranging from 0.86% to 5.81%. The detection rates in Chinese bayberry, fresh D. officinale, and dried D. officinale were 97.92%, 49.29%, and 50.71%, respectively. The dietary risk of metalaxyl residues in Chinese bayberry, fresh D. officinale, and dried D. officinale was acceptable for consumers.