Hi,
if I want to add a new service ,How can I determine the characteristc UUID ?
Are you asking how to select a UUID value? You need to use a 128bit Manufacturer specific UUIDs for a custom defined service. There are UUID generators available on the web. I am not 100% sure if the UUID needs to be registered anywhere but I think the idea is that with 2^128 possibilities, its unlikey you will ever end up with the same UUID as someone else in range.