For cotransformation to work you need to fulfill the following criteria:

1)The plasmids should have different selection markers.

2) The plasmids should have different origin of replications.

Your plasmids have the same selection marker i.e., Amp... Try cloning one of the genes in a plasmid with a different selection marker, say pET28a with Kan.

Apart from this, you can use pETDUET vector which has two cloning sites in the same vector.

Sorry i forget to mention, I'm using pBAD33gfp under ara promoter(chloramphenicol) antibiotics and pRSET having T7 promoter (ampicillin antibiotics) getting on colonies on double antibiotics plate. How can i test for presence of both plasmids in the cell other than growing on double antibiotic plate.

Your problem has two causes:

1- Cells transformed only with pBAD33gfp will satisfy your selection criterion (AmpR+CamR). Also, they will probably outgrow co-transformed cells, given enough generations.

2- The transcription levels of T7 promoters are so high (See the original Studier/Moffat paper, PMID 3537305), that even in cells where cotransformation was successful, transcripts driven by the Ara promoter will be vastly outnumbered.

Hence, you see expression only from pBAD33gfp (case 1) or from pRSET (case 2).

Hope it helps.