Yes, you can extend your Tier 2 visa in the UK if you change employers, however there are specific requirements and steps that need to be followed with your current employer and your new employer. Before deciding to change UK employers, it is important to ensure that you seek legal advice and check the Gov.UK website of any changes and meeting the requirements. 

Original Source:- https://sites.google.com/view/mylegalservices/blog/can-i-extend-my-tier-2-visa-if-i-change-employers?authuser=0