After working for my employer for more than 2 years with H1B visa, I recently get promoted as a group manager with more job duty. Can I use my experience with current employer to apply for the PERM Labor Certification?

Using on-the-job experience in a PERM Labor Certification application may increases the risk of a DOL audit, and may decreases your chances of approval. However, it should not always be ruled out. 

The DOL wants to see a comparison of the job duties of both the job in which the experience was gained and the newly-offered position described in the PERM Labor Certification. This comparison should include the percentage of time devoted to each job duty. Additionally, the DOL will want to see an organizational chart, to identify where the positions fit within the company's various divisions and where the jobs fit in comparison to each other. The DOL also expects to review the company's payroll records, which, in many cases, will reflect raises appropriate for job promotions. 

The best chances of success in cases of this type involve a material change in the nature of the position, and, for H1B workers thus would require amending the H1B petition to reflect the change. Other, typically more successful cases involve changes from initial, lower-level positions, moving up the ladder into managerial roles or changing from one job family group of similar occupations to another and being promoted.