This study developed an instrument to evaluate student online information searching strategies based on a framework comprising three domains and seven aspects. Two versions of the Online Information Searching Strategies Inventory (OISSI), including both quick and complete versions, were finally established and exhibited good validities and reliabilities. The quick OISSI included 13 items and the complete OISSI included 25 items and the pair had total reliabilities of 0.85 and 0.91, respectively. This instrument provides researchers a valid and reliable tool to evaluate students' self-reflected web search strategies. The OISSI scores of 324 high school students revealed a significant gender difference in both behavioral and procedural domain strategies; however, no significant difference was observed in metacognitive domain strategies. In addition, student weekly online searching hours were found to significantly impact only behavioral domain strategies but not other domain strategies, implying that increasing student search experience may be insufficient to lift their search strategy. This study suggested several future study directions. (Contains 11 tables and 1 figure.)