Thank you for your reply.
I have download the the example GRIDMASK file with US states, and knew the header portions of that example file. My problem is I don’t know how the MASK_REGION have something to do with the and the emission grid. Because I make maskfile with m3mask and m3merge for 11 regions,with the suggestion from this forum, such as ISAM SA_ACONC output error - CMAQ-ISAM - CMAS CENTER FORUM. And thank you again for your explanation. But the tracking result for each region is zero. I think the MASK_REGION must be not connected to the emission file’s grid. So I conclude that my MASK_REGION is not correct, and the problem should be the fomat of my maskdata file. Can you tell me what variable should be in the maskdata? I have tried with only COL and ROW, and also don’t work. Look forward to your reply, thank you.