@Yiwei3 You can't get a review removed pre-emptively without knowing what it said. What you should do is go ahead and submit a concise, honest, factual review of your experience with these guests, at which point both will be published and you'll be able to see what they wrote.
If the guest's review clearly violates the content policy you might be able to get it removed. But this is relatively rare. So be prepared to write a Host Response to correct any inaccuracies or put negative comments into context, with your prospective guests in mind as the audience. One of the biggest mistakes hosts make with negative reviews is writing responses that make them look angry and vindictive; be sure to avoid that trap by responding in a way that demonstrates your grace and professionalism.