Your portfolio shouldn't consist of architecture stuff if you don't have an architecture background.  The main point of the portfolio is showcase your creative and artistic skills.  Drawings, sculptures, things you've built, paintings, etc. are all fair game.

My portfolio for entering undergrad was 100% non-architectural photography.

@zenza Thanks for the advice! But I'm not sure if this is the same situation for a Master Degree.... I can barely see any drawings and paintings in the portfolio in this forum ...

I recently applied and was accepted into the M.Arch program at UT Austin. I didn't have a background in Architecture - my Bachelor's was in mechanical engineering. I participated in a summer introduction to architecture program at the University of Illinois - Chicago, and built my portfolio mostly around the work I did there along with some sketching I'd done and a light sculpture I built.

If you have the opportunity to participate in one of these programs I'd highly recommend it. Schools all across the US have these including but not limited to Harvard, Columbia, and UT Austin. They really give you an idea of what to expect in graduate school and help you determine if you really want to go. They also give you plenty of material for your portfolio. 

My MArch portfolio was mostly theatre stuff, no architecture except some random CAD dwgs.

Its the same. Many people get into M.Arch without architecture stuff. Many times, those people have the most interesting portfolios since many architecture students get lost in code/detailing/zones etc. Just put anything that interests you, photography, stuff youve made and you will be fine! Don't start purposly modeling buildings just for the portfolio. Its not going to catch their eye. At most you would have created a zaha building...

Thanks guys I feel more positive now!

I will look for some those program definitely!