I have a interview next week at a pharma industry how should I prepare for the technical round. What ground should I cover based on my subject

Pharma companies would be recruiting mechanical engineers to work on boilers, AHU, HVAC, Chiller, compressors and other process equipments. Perhaps you could brush up your skills on those topics and be sure to go through all the engineering topics once. 

You did not mention if you are experienced. For experienced professionals, you should be confident while answering the projects that you've worked on so far. Be assured that the interviewers will definitely want to know what kind of work you've done so far and what exactly have you mentioned in the resume. 

Give a thorough look at your own resume and the skills / work-experience / education that you've mentioned. Your resume is the first document that the recruiters are most likely to refer to and base their initial questions. 

Other than that, also go prepared to answer questions specific to their industry and the role that you are applying for. 

I hope this helps a bit. Wish you all the best. Do keep us posted on your progress.