I want to reset MCU by software,How can I control the register?
You can check in the Cortex M0+ :
AIRCRa Application Interrupt and Reset Control Register in the ARMv6-M Architecture ReferenceManual.
Checking in the ARMv6-M RM :
In the AIRCR register, WO - SYSRESETREQ bit. : Writing 1 to this bit asserts a signal to request a reset by the external system.
This register is in address : 0xE000ED0C
So you should write the bit  SYSRESETREQ in that address to request a SW reset. Take care with the rest of the bits value, modify only that bit.
Retrieving data ...