I have seen a kind of dance in America or Britain's got talent show, like slow motion. What's the name of that dance, or give me a link to that video, thank you.

This is a branch style of Poppin, called "SlowMotion", which is now classified as animation style. This requires excellent control of the body and coordination of expression and breathing. The representative figure of this style is the master Phax. You can download it from Baidu and it will definitely surprise you.