Reviewer comments are in complete contrast about research article Recently my research article has been reviewed after first round of revision and has been sent back to me by editor. In addition, editor has written in a very clear manner that a thorough response and revision will make my paper eligible for second round of revision otherwise it would be a waste of time. 
In the light of reviewer's comments, one reviewer has completely recommended the paper and didn't ask for any change but what surprised me the most was other reviewer comments as he hasn't recommended my article for publication. both reviewer comments are complete in contrast with each other.  for example, if first reviewer is telling that research article has explicitly stated its significance the other reviewer has stated that it is missing significance.

my question is, can i email editor to change this reviewer and request him to look for other reviewer although editor had told me before the reviewer in my field are not much in number. or just simply withdraw my paper from this journal?
Since it was the editor that said you need a thorough "response", I think you need to revise. It sounds like s/he is trusting the second reviewer. Think especially about the significance. It may be that it is there, but you didn't state it clearly enough. 

I doubt that the editor will respond favorably to such an email. Just re-think your  paper and do a revision. You don't need to explicitly change it for any particular reviewer comment, but you need to consider what the reviewer has said and how you can improve it if possible. 

It may just be that one of the reviewer (either one) has missed something, but you don't really know which.