I know somebody back china by using chinese passport even they oathed as canadian citizenship. the reason is you don't have enough time to get the new passport yet. so it is reasonable to use the old one. But I don't know how they come back yet.
Now when you travel to US, the passport of canada is necessary, citizenship card is not enough anymore.
进去宣誓的时候枫叶卡就收走了。出来的时候拿到的是成为公民的那张纸。It was ok when there was still landing paper years ago. They don't take away your landing paper when you become citizen. So you can go china using chinese passport and back with landing paper.
If you still has maple leaf card valid and your chinese passprot valid, you should be back to china without problem. If you don't have your maple leaf card then forget about it. I believe they take away your maple leaf card when you become a citizen.
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Have a nice trip and share your experience if you do go as PRC citizen and come back into Canada as Canadian citizen.