Thanks a lot for your response, Daniel.
My purpose is to make nifti pairs which has the same geometric parameters as another set of data (-geomparent). ( not convert a NIFTI format dataset to AFNI format). Sorry for confusion.
But I found that to3d did not work with -geomparent geomparent .hdr although to3d works well with -geomparent geomparent+orig.HEAD.

In other worlds, for example, this command will not working.
to3d -prefix test.hdr -time:zt 31 4 2800 alt+z -geomparent geomparent.hdr 3D:0:0:128:128:124:data

This command works,
to3d -prefix test.hdr -time:zt 31 4 2800 alt+z -geomparent geomparent+orig.HEAD 3D:0:0:128:128:124:data

I guess that -geomparent option does not support its files in nifti pairs

Thanks.

Jian