I want save solidworks 2016 part file in solidworks 2015 as like autocad ?
There is no backward compatibility with regards to the parametrics in SW. All you can do is export the 2016 file (step, iges, parasolid) and import it into 2015, it will be a 'dumb' solid at that point and hopefully you can work from there.
Dear Robert i know very well this type method thanks for suggestion but i want on solid works format file. if any another suggestion please share to me
It will be a solidworks format after you save the imported file, i.e. sldprt or sldasm, but you won't have any feature history.
You can't do it.
If you have the latest service pack for 2015 installed (5?), 2015 might open 2016 files, but I've had mixed results.
I don't think it would be worth the effort, but you could use the Feature Recognition tool in SolidWorks when importing a "dumb solid" into SW2015.
Users have been asking for backwards compatibility for two decades. The closest we have is using the latest service pack in the previous year's release. Beyond that, you'll get the "future version" error.