I have had surgery twice of the parotid gland(pleomorphic adenoma). now from last 1 month my intra parotid lymph nodes are swollen, why?

Many possible reason: If you are certain this is an intraparotid lymph node (as opposed to a nodule of recurrence of pleomorphic adenoma), there could be many possible causes ranging from some infection, to inflammatory diseases either specific to the parotid or more general, to some other tumor. The person who did your most recent parotid surgery is probably in the best position to answer this question.