As one of B-learning practice, mixed peer response groups consisting of both native English speakers and English as a Second Language (ESL） students are often seen in mainstream ESL composition classes. A few researchers have examined the effects of peer feedback on writing skills, language and cultural awareness of ESL students in mixed groups, but little research has explored the similarities and differences of peer feedback types in a mixed group. The study investigates Sino-US peer feedback types in a Cross-Pacific online exchange by contrasting their distributions and frequencies as well as learners’ reflections around feedback. Data included peer feedback discourses, review reports and a follow-up interview, which reveals no significant differences of peer feedback types between Chinese learners and American learners, showing critical feedback the largest, followed by affirmative feedback and others. However, their frequencies of types of peer feedback are significantly different in three aspects, including criticism vs reader friendly, authoritative dialogue vs equal dialogue and static text vs dynamic discourse.