Based on 312 samples, this study investigated the relationship between two dimensions of L2 vocabulary knowledge (VK) and listening comprehension (LC) by comparing written and oral vocabulary measurements and further examined the mediating effect of L2 vocabulary fluency (VF) by using Bootstrapping and Monte Carlo Method. Results show that: (1) the regression coefficient from written receptive breadth and depth of VK to LC were [beta] = 0.29*** and [beta] = 0.22***; (2) the regression coefficient from oral receptive breadth and depth of VK to LC were [beta] = 0.34*** and [beta] = 0.31*** ; (3) the variance explanatory power of LC reached 64%; (4) VF played a partial mediating role between VK and LC; (5) on the condition of the mediating effect of VF, regression coefficient of written receptive vocabulary breadth to LC increased by 13%, reaching [beta] = 0.42***, that of oral one to LC raised by 17%, reaching [beta] = 0.51***; and (6) regression coefficient of written receptive vocabulary depth to LC increased by 19%, reaching [beta] = 0.41***, that of oral one to LC raised by 15%, reaching [beta] = 0.46***. Finally, we discussed respective importance of different dimensions of VK in LC. The conclusion of the study was of significance to teaching of L2 VK and LC.