I have an experience like of around 6 years as an iOS developer but I am feeling like stuck. Is there any certification for iOS developer which can help me in getting better job or which can put me in the priority list of recruiters?
Getting certification for completing coursework and getting hired aren't necessarily at all related endeavors. If you have been developing for some time, then ideally you have something to show on your resume and CV which will reflect not only your relevance in the marketplace, but also your potential value to the company you are applying to and hopefully interviewing with. For example, your projects on github and other verifiable accomplishments clearly demonstrating your skill set.
As for certifications with recognized market value, I suppose a good start would be Apple's website portal: http://training.apple.com. Specifically for iOS development certification, there's Apple's "Global Authorized Training Provider" Learn Quest.
It certainly couldn't hurt to learn the programming language Swift. I don't know that they have a certificate optionStanford offers a course through iTunes for iOS10. There's also the main Swift site and Apple's Swift Developer site.
...and there's online course certificates from places like Udacity: https://www.udacity.com/course/ios-developer-nanodegree--nd003
Note that Udacity's "nanodegree" program and other certification programs (including bootcamps) claim varying degrees of "money-back" and other such guarantees if the certification doesn't lead to some kind of employment (which might simply be teaching the courses). The folks I know personally that have gotten hired to full-time jobs have paid for bootcamps and gotten jobs through the contacts they've made there.
As for getting noticed by recruiters, there is LinkedIn.com and job sites like Indeed.com. Networking, however, cannot be under-rated. Find local developer groups and meetings and get to know who the people in your area are. If you've gone to college, community schools, etc. use those resources as well.
Hope that helps!