Hi Dawei,
I'm really sorry for how you feel towards the support that I've provided you. I spent a lot of time trying to reproduce the error and looking for the best way to solve it.
I understand that the answer I gave to you might no be the one you were expecting and now that I looked back I realized something I missed the first time
What is the value for you shunt resistor? In the picture you sent me I see you connected one between ISENSEH and ISENSEL. Just as is shown in this diagram:

I'm asking you because there is one register you need to configure in order to make proper current calculations. In the Datasheet for MM9Z1_638 in Table 199: Temperature filtering period (COMP_TF) - register field descriptions, you will find a register named IRSEL, this the register you need to configure according the value of you shunt resistor, because the current calculations are made by measuring the voltage drop VDROP over the external shunt resistor (connected to ISENSEH and ISENSEL) and the value of IRSEL.

Thanks for your feedback, and if there is anything where you think I should improve, just tell me and I'll be glad of working on it.
Best Regards,
Dario