Task motivation is critical to learners' task performance. However, scant studies have examined learners' task motivation in the translation continuation task based on the "xu"-argument, an emerging view on language acquisition. This exploratory study examined how Chinese English as Foreign Language (EFL) learners' task motivation changed in ten translation continuation tasks and what factors contributed to the changes. Five second-year students in a Chinese university participated in the study and they were requested to perform one translation continuation task each week over ten consecutive weeks. Task motivation questionnaires were distributed after each task. Interviews were conducted in the fourth week and the last week. Results showed that participants' general task motivation across the ten tasks exhibited a "high-low-high" changing pattern. Factors accounting for task motivation fluctuations were categorized as learner-level, task-level, and post-task-level, wherein topic selection and content features played the most prominent roles. Two representative learners were identified due to their higher- or lower-than-average task motivation levels in most tasks. The findings offer pedagogical insights into improving task motivation and developing learner-specific strategies for translation continuation tasks.