Thanks much for the info. What if she already have a visitor visa and after marriage she come with me to Canada with her visitor visa and apply PR from Canada? if yes, will she able to get an extension of her visitor record(beyond 6 months) if her PR is still in process.?
ok for you to understand better.
People that come to Canada on TRV (temporary resident visa) be it studies or work are seen as somebody who will leave Canada sooner or later. So in that perspective it is a bit easier to get their visitor visas approved. Additionally in those cases they can apply for spousal work permit (a temporary work permit).
In your case, the situation is different. You are PR, which means that you are not gonna leave. Your spouse (and kids) is your closest family as you are hers. In that light of course she would not want to leave once here TRV is done, so in order for them to minimize the hassle later on, they just deny them on the spot. And yes they know that there is a chance, that you want to sponsor her, but they do not know just looking on you and her if that will ever happen and if you are even eligible to sponsor her or if she is eligible to be sponsored.
If she already has a TRV that is good, just be warned, that even with those she can be rejected on point of entry. Yes they do ask about things like purpose of your stay and where will she stay and lying on those questions is a short way to application rejection later on.
So that is why people here are hinting you to be ready to be app. 1 year apart (for standard cases where you are eligible and she is as well).
You might think, that 1 year (maybe even less) is a long time. Actually it is not, it will pass pretty fast.
Of course she can try her luck and use visitor visa once you are married, just be aware what can happen on border crossing. If she will make it through, then you can apply for inland sponsorship and for her spousal work permit (takes about 4 months to get that permit) while waiting for that sponsorship to happen.
Good luck