Abstract: To further testify the validity of the"Involvement Load Hypothesis", this paper examines the general effect of threedifferent involvement loaded reading tasks on incidental vocabulary acquisition, and studies their different degrees of target wordacquisition. Results show that task involvement load had significant effects on both the general effect of vocabulary immediate anddelayed retention, and the lexical learning degree of target words. According to the findings, some pedagogical suggestions are given forthe future lexical teaching and learning in China.