If you want to work in Canada after you graduate from your studies, you must apply for a work permit under the Post-Graduation Work Permit Program.

Post-Graduation Work Permit Program

The Post-Graduation Work Permit Program allows students who have graduated from a participating Canadian post-secondary institution to gain valuable Canadian work experience.

A work permit under the Post-Graduation Work Permit Program cannot be valid for a longer period than the length of your studies. For example, if you graduate from a four-year degree program, you could be eligible for a three-year work permit if you meet the criteria. If you graduate from an eight-month certificate program, you would be eligible for a work permit that is valid for no more than eight months.

Source: http://www.cic.gc.ca/english/study/work-postgrad.asp