Somewhere in your file there must be a line with 8 columns. This will be the one just before the first warning about 7 columns. I would guess this should be the first line with data. What are the first few line in your file?
Thanks for your reply.
I have solved the problem.
There are really only seven columns in the xvg file, but I generated the file in windows, and the encoding format is UTF-8. However, in Linux, the required file encoding format is UNIX, so eight columns are recognized