Thanks for your reply. I tried to use mri_surf2surf function to convert my .w files to .mgh/.mgz files, and both cannot be imported as texture in brainstorm.
I can import the surface files from freesurfer, such rh.inflated_avg, lh.inflated_avg... in freesurfer7.2.
My problem is I cannot import .w file which is generated by freesurfer using mri_surf2surf function.