When I took mine, I just call the 1-800 number listed on:
and register my exam online at http://www.2test.com (a prometric site).
Unfortunately, China is not listed in the locations you can register the exam so I think you have to shell out RMB1250. Or, if you can, you might try to take the exam at Hong Kong, it is listed in the exam locations. But I don't think it's going to worth it since the air plane ticket price would be more than the cost of exam voucher.
Or, you can take the exam after you come to Canada. At first I didn't know it was Canadian $150, I thought it was US. But after I got my credit card statement, it was just Canadian $150. I think they calculate the price according to US$150, which is around RMB1250.