Fibroblast growth factor 18 (FGF18) is a member of the fibroblast growth factor family and important in cartilage growth and development. However, the mechanism by which FGF18 mediates its biological functions is still unclear. In our study, we expressed the rhFGF18 protein fused to a HaloTag, (Halo-rhFGF18). mrr assay results indicated that both rhFGF18 and Halo-rhFGF18 have similar biological activities in NIH3T3 cells. However, basic FGF and acidic FGF were more potent than both rhFGF18 and Halo-rhFGF18. Confocal imaging data indicated that the red fluorescence labeled Halo-rhFGF18 strongly bound to ATDC5 cells and stimulated their proliferation and differentiation, which suggests that glycosaminoglycans may be involved in mediating the biological effects of rhFGF18 in ATDC5 cells. Moreover, western blot results demonstrated that, in ATDC5 cells, ERK1/2 signaling is activated upon stimulation with rhFGF18. Our results may open doors for the use of rhFGF18 as a drug to promote cartilage growth.