I have a nintex form with 20 people picker control and the page load takes 14 seconds to load .Is there any way I can control this page load time .?.Any suggestion .
Check out this post for techniques on how to improve forms performance. 20 person picker controls is definitely going to add some overhead to your forms loading time.
Also you might want to check that your Nintex data centre is the same as your o365 data centre. You can check which Nintex data centre you are using via your Nintex gallery page - go to the about section where it tells you your tenant ID. It will also specify which data centre you're using. If it's different to your o365 data centre, you can request that it is moved which will help performance.