Hello.
I’m an international student and want to apply for PhD CS to U of Waterloo. And i’m plan to stay in Canada.
How is the job market for a PhD graduate from Waterloo?
Do you suggest applying for second master degree?
Thanks.
The job market for CS from Waterloo is excellent and Canada loves international STEM graduates. 
Now the issue is to get admitted.
As you assess this question, it might be wise to understand fully that the post-PhD job market – in general – is VERY roughly divided into academic and non-academic spheres (for profit commercial/consulting/research enterprises, public service, non-profits, and so forth). Obviously, a good deal of overlap exists between these two sectors and people frequently move between them. However, I mention this because a university may have much stronger placement in one or the other sector, and that might be important for you to ascertain.
None of the foregoing is specific to CS or to Waterloo.