Hi Wei,
Greetings from Syncfusion support.
Based on the provided information we tried to
reproduce the reported issue, but we were not able to replicate the issue from
our side. We have attached the screenshot for your convenience. Please share
the following details so that we may be able to provide a better solution ASAP.
Please
share a sample to replicate the issue.
Please
confirm you are not having any columns that are hidden in the screenshot you
have shared.
Please
share the Syncfusion package version you are using.
Screenshot: 
Note: By default, in EJ2 grid the height of the header
row will be adjusted automatically based on the height of the content.
Please get back to us for further details.
Regards,
Joseph I.