This study examines how the genre of input text influences Chinese young EFL learners' performance on continuation tasks. Participants were 30 students in Grade 9 and repeated-measures design was adopted to compare their performance on narrative and argumentative continuation tasks, in terms of writing quality, CAF indicators as well as alignment. Results showed that (i) genre had no significant influence on students' scores on the two continuation tasks; (ii) argumentative continuation task brought about more complex sentences and words, as reflected by most indicators, but narrative continuation task led to relatively longer writing, and no significant difference was found for accuracy; (iii) students' writings on argumentative task contained more 4-word phrases that were drawn from the input text, while the writings on narrative task were semantically more related to the reading input. This study provides another piece of validity evidence for employing continuation tasks in different genres in language tests and has implications for the writing teaching of Chinese young EFL learners.