It will depend on the program you are looking to apply and the time left for your graduation.
When you study full time you are not allowed to work, which make things harder. One of the requirements for PR is to show that you have the financial means to support yourself and your dependents. There is a list on the CIC site which gives you a pretty good idea of the minimal amount of money you will need for 1 year.
Also some of the programs have some kind of restriction if you apply as an economic immigrant, and that is that in order to contribute with the economy of the country you should integrate into the labor force. If you are studying you wont be able to pass that requirement.
I would strongly suggest you, to wait until you finish your studies in order to apply, but before that, start getting job interviews, getting an IELTS (expires in 1/2 years, so time it right) and translation of non English documents like birth certificates, etc.
