Immigrant question: Definition for similar job in AC-21 after 485 180 days pending?

Question

my 485 is already pending 180 days, and try to change job according AC-21, which type job can be the similar position?

It is hard to find some new job with the same title and job description.

Answer 1

See the USCIS guidance
http://www.uscis.gov/files/pressrelease/AC21Intrm122705.pdf

Question 3. What is “same or similar” occupational classification for purposes of I-140
portability?
Answer: When making a determination if the new employment is the “same or similar” occupational
classification in comparison to the employment in the initial I-140, adjudicators should consider the following factors:
A. Description of the job duties contained in the ETA 750A or the initial I-140 and the job duties of the new employment to determine if they are the “same or similar” occupational classification.
B. The DOT code and/or SOC code assigned to the initial I-140 employment for petitions that have a certified ETA 750A or consider what DOT and/or SOC code is appropriate for the position for an initial I-140 that did not require a certified ETA 750A. Then consider the DOT code and/or SOC code, whichever is appropriate for the new position to make a determination of “same or similar” occupational classification.
C. A substantial discrepancy between the previous and the new wage.

You can find SOC occupational codes here:
http://www.bls.gov/soc/soc_majo.htm

Answer 2

check out www.immigrationvoice.org. It is website by skilled worker immigrants. You will find lots of valuable information on AC21 there.