I'm not sure you can do it by an automatic script; if there is one, the gormacs or other MD users can be helpful - if not, you may prepare a house script to calculate it using the MD trajectory frames.

Dear Roja,

there are some tools for analyzing water molecules in Gromacs, consider evaluating the "gmx hbond" and the "gmx h2order", maybe there is the code you need. To analyze angles, in gromacs there is the "gmx angle", but an index is needed.

Thank you dear @ranylson have you ever try these tools?

I've try them, but they don't give me the proper result. I used 'gmx gangle' instead of 'gmx angle' because i want to calculate distribution of beta and alpha angles(in figure1, but....

The process of using gmx gangle was really confuing for me...

I agree with you in making soecial index, but how should i define the OH bond and HOH plane by gmx make_ndx? ? That's the main problem' defining alpha and beta'

Best