The continuation task, a reading-to-write task that requires students to make the given plot a complete story, is gradually gaining prominence in the National Matriculation English Test in China. Previous empirical studies revealed that alignment effect existed in the continuation task and as students with different proficiency levels actively interact with the source text, their writing performance was facilitated. The present study attempts to investigate whether a more sophisticated vocabulary prompt could facilitate EFL learners' writing performance in the task, specifically from the perspective of lexical complexity. Our findings confirmed the expected alignment effect and discovered that greater lexical complexity resulted from an increase in the concreteness and imageability of the content words, which was viewed as an evidence of a better grasp of the nature of narrative writing required in the continuation task. In addition, the results suggest that the alignment effect is formed due to the activation for more concrete scenes.