Abstract：Abstract: L1 thinking has been of critical interest in L2 writing research. However, how to manipulate a L2 context that helps mediate the effect of L1 thinking and promote idiomatic expressions, still remains perplexed and controversial. This study investigated how L1 thinking was involved in and influenced the writing process of the continuation task through think-aloud method and retrospective interview. 46 participants were randomly assigned to three groups: to read an incomplete story in English and continue it in English, to read the Chinese version of the story and continue it in English, and to read three successive pictures version of the story and continue it in English. Results show that all participants used L1 in their L2 composing process, although their amount of L1 thinking varied among different thinking activities. In addition, modes of input (L2 input, L1 input, picture input) of the continuation task had effects on L1 thinking in L2 writing, while L2 input elicited the least L1 thinking. Finally, the amount of L1 thinking appeared to be negatively related to L2 text length. These findings indicate that the continuation task can decrease the learners’ reliance on L1 thinking and L1 contextual knowledge by providing an authentic L2 context and scaffolding assistance. Key Words: the continuation task; L1 thinking; L2 writing; contextual knowledge
