By using the eye-tracking method, the present study explores whether working memory capacity assessed via the second language (L2) reading span (L2WMC) as well as the operational span task (OSPAN) affects the processing of subject-extraction and object-extraction in Chinese-English bilinguals. Results showed that L2WMC has no effects on the grammatical judgement accuracies, the first fixation duration, gaze duration, go-past times and total fixation duration of the critical regions in wh-extractions. In contrast, OSPAN influences the first fixation duration and go-past times of the critical regions in wh-extractions. Specifically, in region 1, (e.g., Who do you think loved the comedian[region 1] with [region 2] all his heart [subject-extraction]? versus Who do you think the comedian loved [region 1] with [region 2] all his heart? [object-extraction]), participants with high OSPAN were much slower than those with low OSPAN in their first fixation duration in reading subject-extractions, whereas there were no differences between participants with different OSPANs in reading object-extractions. In region 2, participants with high OSPAN were much faster than those with low OSPAN in their go-past times of object-extractions. These results indicated that individual differences in OSPAN rather than in L2WMC more strongly affect processing of wh-extractions. Thus, OSPAN results to be more suitable to explore the influences of working memory while processing L2 sentences with complex syntax, at least for intermediate proficient bilinguals. Results of the study also provide further support for the Capacity Theory of Comprehension.