We have proposed and experimentally demonstrated a scheme for cascading four-wave mixing (CFWM) by exploiting nonlinearity in highly nonlinear fiber (HNLF). Through utilizing optical spectrum analyzer (OSA), the second-order sideband products are observed in our experiment by only launching two waves into HNLF, and the conversion efficiency from the injected wave to each sideband is discussed in detail. It is found that only the conversion efficiency of the satellite wave will be increased with the power of the tunable injected wave when the power and the wavelength of the other one are fixed. Furthermore, the conversion efficiency of all the sidebands will be decreased with the absolute value of detune of injected wavelengths increasing. Also, the authors have demonstrated that the power of the satellite wave will be influenced most among all the sidebands if tuning the injected wave power. The proposed scheme can find potential applications in parametric amplification, frequency conversion, and optical quantum-information processing.