HI @xiaomeng.zhang ,

Thanks for writing into the Community! Denis here, happy to help!

I use Stickiness, If I set it like the picture above,   is it new user in first 30 days . right?

Here we are looking for anyone who was new in their first 30 days and did a New User event. Please note, a New User event is any event done by the user on their first calendar day of use. So if someone joins Amplitude today at 2pm and they trigger three events at 3pm, 5pm and 11pm, they will have 3 new user events for today as they triggered three events on their first day of use. 

and the follow picture is 95.8% new users in first 30 days,  open our webside one day

Yes, 95.8% of New Users open your application and fire any event on Day 1. 

If I use the wrong method, is there any way to check the first 30 days of new users in stickiness

This should be fine. It will get the users who were new in the Last 30 days (and within the date range you specified on the chart) and will show on what days these new users come back to fire any event.

I hope this explains it well enough for you! Let me know if I can clarify any further!