To present a case with progressive keratoconus after treated with radial keratotomy (RK) and was undergone corneal collagen cross-linking (CXL) for preventing the progress of keratectasia. A progressive keratoconus case who was previously treated with RK was undergone corneal collagen cross-linking (CXL) in her left eye for preventing the progress of keratectasia. After the CXL procedure performed at another clinic, best-corrected visual acuity (BCVA) of her left eye decreased from 0.9 to 0.6 Snellen lines in an 8-months follow-up. Pre CXL maximum keratometric power (P-Kmax) was also increased from 52.1 to 57.16 Diopter (D) in the eight months after CXL. Applying CXL on the keratoconic patient previously treated with RK should be questioned.