BQ27220: how to use BQ27220?

See my comments below.

(1)Where should VSYS be connected?

I would suggest you take a look at the BQ27220EVM schematic.

(2)Is GPOUT enable? In the datasheet, it says output.

See Page 4 of BQ27220 for the details. 

(3)Is this power supply BAT pin? (In that case if the battery is connected to BAT pin, the consumption current will always exist?)

As we mentioned int the datasheet, the BAT pin should connect to the positive battery terminal.

4)Could you explain the detail on what is SRN pin and SRP pin?

(5)Is the connection between SRP pin and BAT pin short?

 See Page 4 of the datasheet.

(6)VDD pin is just LDO1.8V output?

 See Page 4 of the datasheet.

(7)What is the max of current consumption for each mode?

 See Section 6.5 of the datasheet.

(8)It says if the thermistor will not be connected to BIN, it will pull down. In this case, is there any affect to the detection of battery level?

 No. If the battery pack thermistor is not connected to the BIN pin, the BIN pin should be pulled down to VSS with a

10-kΩ resistor.

(9)What is the maximum output current of VDD?

As we mentioned in the datasheet,  the VDD pin is not intended to provide power for other devices in the system.