I want to write datasheet for a product.
Is there any software support typical datasheet writing?
AFAIK, there is not.
And I don't think there is any real need for it either.
Assuming you are writing for engineers, they will be more interested in
accurate and useful information rather than the style.
If you are writing sales leaflets, then style might be important.
Why not say to your own engineers,
"If you were evaluating this product, what do you think you should know
about it in order to understand and use it? And write it down."
I'm guessing by your email address that you are oriental.
Your writing is not fluent English, so if you want the data sheet in English
you should get a native English speaker to check the final text. I've seen
quite a few data sheets where the text has been so appallingly bad that it
cannot be understood.
The Japanese are particularly prone to writing English text and assuming it
is correct or makes sense. See:
http://www.engrish.com/