Most L2 learners cannot process a second language as native speakers do because of their less automatic syntactic processing ability. In this article, the author reports two experiments that used a word-by-word self-paced reading task to examine how Japanese language learners of English process English prepositional phrases. The study also examined whether these learners could improve their syntactic processing ability, using the priming method. The research findings showed that while L2 learners had more difficulty processing a prepositional phrase when it modified the noun of the matrix verb than modified the verb, they were able to overcome that difficulty with appropriate primes. The research findings indicated that L2 learners were able to improve their syntactic processing ability... if they encountered the same syntactic structure repeatedly.