Dendrobium plays a key role in the orchid industry, with ornamental, medicinal, and economic value. Recently, we found a newly recorded boring pest damaging Dendrobium in Guizhou Province, China. The species is identified as Nassophasis sp. (Coleoptera: Curculionidae: Rhynchophorinae) by morphological and anatomical features. The occurrence and biological characteristics of this species were verified through field investigation and indoor experiments. The results showed that detailed external morphological and genitalia characters and male-female differences are described to identify Nassophasis sp. The pest produces three generations per year, with overlapping generations. The adults overwinter in the root stains of Dendrobium and emerge in mid-March of the following year. Adults feed on stems, leaves, and flowers, often laying their eggs inside the stems; larvae then bore into the stems causing decaying and hollowing until complete immature development. There are three larval instars, grouped according to their head capsule width and body length, which were measured following Dyar’s law and Crosby’s law of growth and showed a significant linear regression (p < 0.0001). The results of this study provide a theoretical basis for the prediction and comprehensive control of the insect.