This study investigated the effect of boundedness on countability by analyzing English learners' use ( misuse in particular) of nouns． The results show an obvious influence of L2 learners' boundedness construal in that in terms of countability， the accuracy rates of bounded nouns are significantly higher than those of unbounded nouns， and the developmental patterns emerging from the accurate rates of bounded and unbounded nouns used by English learners of different English proficiency levels are of total difference， while the patterns for the different kinds of bounded /unbounded nouns are remarkably similar． It is found that the shift in boundedness of a noun and different construals of English and Chinese people result in learners' high cognitive load， thus giving rise to errors in countability． The influence of boundedness is also observed to change from interlangauge one to intralanguage one．