<p>This study compares the processing strategies of 62 Chinese English as a Foreign Language learners when processing English object relative clauses (with filler-gaps) and appositive clauses (without filler-gaps). Through self-paced reading tasks, advanced L2 learners demonstrated a faster processing speed for object relative clauses compared to appositive clauses. Conversely, intermediate-level adult learners exhibited no significant processing differences between two types of clauses. A word decision task further proved that the difference in processing is due to syntactic processing strategies, rather than lexical factors. Findings suggest that L2 learners can utilize the Active Filler Strategy for filler-gap dependencies in a way similar to native speakers, despite syntactic differences between their L1 and L2 relative clauses (head-final vs. head-initial structures), and that L2 proficiency is a significant factor. The study highlights the role of L2 proficiency and addresses a research gap in understanding L2 processing strategies for filler-gap dependencies.</p>