[Objectives]  Protease inhibitors and cucurbitacins are two kinds of insect-resistant compounds in plants that are important in the interactions between herbivorous insects and their host plants. We studied the effects of Liriomyza huidobrensis (Blanchard) larval infestation on the activities of protease inhibitors and cucurbitacin B content in cucumber leaves in order to investigate the mechanisms of interaction between the leaf miner and its host plants, and to build a necessary foundation for use of inducible resistance to control the leaf miner. [Methods]  Spectrophotometry was used to determine the changes of the activities of protease inhibitors and High-Performance Liquid Chromatography (HPLC) to determine the cucurbitacin B content in cucumber leaves. [Results]  The activities of trypsin and chymotrypsin inhibitors, and the cucurbitacin B content in cucumber leaves increased during larval infestation (1-9 d), compared to control plants, but the magnitudes of these increases were not consistent with the infestation levels and durations. Induction of the trypsin inhibitor was systemic while induction of the chymotrypsin inhibitor and cucurbitacin B were not. [Conclusion]  Larval infestation can induce an increase in protease inhibitor activity and cucurbitacin B, and the breeding of cucumber varieties with inducible protease inhibitor and/or cucurbitacin B may be an effective approach for controlling the leaf miner.