On the basis of Long’s Interaction Hypothesis, Vygotsky’s Social Interactionism and the theory of noticing from cognitive psychology, the research explored types of output modification moves used by Chinesespeaking learners of English，and the impact of task type on modification moves and correct language production in L2 learning. The results from the observational study showed that the Chinesespeaking learners of English used 10 types of modification moves in their interaction with peers, including confirmation checks, clarification request, comprehension checks, selfcorrection, othercorrection, repetition, scaffolding, metalinguistic talk, solicitation of assistance and unsolicitated explanation. We believe that these modification moves may ‘push’ learners to improve language production, and may help them to reconstruct their interlanguage system. The second study examined the effect of task type on the amount of mutual scaffolding and oneway scaffolding moves used and correct use of language, which produced these findings: (a) in contrast to the open, optional information exchange task with divergent goals, the close, required information exchange task with convergent goal pushed the learners to use greater amount of scaffolding move; (b) in addition, the close, required information exchange task also elicited more mutual scaffolding move, which helped the learners to integrate greater amount of language into their interlanguage system; and (c) the open, optional information exchange task brought about more oneway scaffolding move, and lower percentage of correct language integration in the delayed test.