This study aims to investigate the relative clause attachment resolution process of second language learners of English from various aspects. Three experiments were conducted: off-line test(Expt. 1), on-line test(Expt. 2), and a quasi-interview survey of their strategy(Expt. 3). As a result, second language learners of English showed different RC attachment preferences from native speakers of English in the off-line test; however they showed similar preferences of NP2 following the recency effects. Also, the different RC attachment preferences were observed between the off-line test and on-line test among the participants, second language learners of English. The results from reading time and responding time measurement in the experiment 2 and the strategy survey in experiment 3 supported these asymmetric results between the two tests. The findings may have implications that second language learners of English do not follow the consistent and complete cognitive process for the RC attachment resolution process.