This study investigated the influence of written corrective feedback under two different computer-mediated environments (synchronized and synchronized) on the acquisition of English grammar in the Chinese English learners. Students from two intact classes (63 in all) were randomly assigned to three different groups: synchronized computer-mediated feedback group (SCF), synchronized computer-mediated feedback group (ACF) and comparison group. Findings show: (1) both the SCF and ACF groups significantly outperformed the comparison group, demonstrating the effectiveness of grammar acquisition of written corrective feedback under two different computer-mediated environments; (2) SCF did not show significant progress than the ACF group, showing that it seems written corrective feedback which is done through the use of text reconstruction task could facilitate the acquisition of English grammar, because this type of task cannot play its full advantage of synchronized computer-mediated communication.