Eukaryotic cells extend a variety of surface protrusions to direct cell motility, which is mediated by coordinative actions between plasma membrane and underlying actin cytoskeleton. Here, we found that with its amphiphilic motif, the single calponin homology (CH) domain-containing protein CHDP-1 anchors on plasma membrane and induces membrane deformation in C. elegans. Through its CH domain, CHDP-1 associates with the small GTPase Rac1/CED-10, which is a key regulator for actin cytoskeleton arrangement. CHDP-1 preferably binds to the GTP-bound active form of CED-10 protein and the membrane localized GTP-CED-10 is decreased when CHDP-1 is removed. Thus, by coupling membrane expansion to the Rac1-mediated actin dynamics, CHDP-1 promotes membrane protrusion in vivo.