It doesn't matter where you are in the world, if an employer wants rid of you, they will find a way.
However, if you have passed your probation period and you get fired for no reason, you can sue your employer and they will have to show that they fired you with a just cause or if they can not, they will have to pay you a settlement. The employer would be expected to show that there were ongoing problems with your performance and that you had been warned a couple of times in writing. That is unless they lay you off because their work has dried up in which case they probably would have to show that the work really dried up and that they did not hire another person to replace you.
In any case, there may also be reasons you might not want to sue your employer. For example, you may work in a narrow job market or live in a small town and you may not want the reputation of suing your employers because it can negatively affect your ability to find a new job. You also might not feel like staying with an employer who you feel does not want you around so before getting booted out, you may quit on your own.
Changing jobs is less of a problem in Canada than in many other countries because the job market is relatively fast and people change jobs often.
