about NLANR

   I used the trace file from NLANR to test Bro. But Bro does nothing but
bad checksum.

That's because those traces don't have any packet contents.

What should I do , to make trace file available to Bro?

You should first consider whether it will be useful to analyze them with
Bro, given a lack of contents.

If so, then "redef ignore_checksums = T" will turn off the checksum tests.