New Year: xīn nián kuài lè (Happy New Year!)

Xin Nian = "New Year"
Kuai Le = "Happy"
Xin Nian Kuai Le = "Happy New Year"

Other Informaton: 

During Chinese New Year, people often use 恭喜(gōng xǐ) to replace "Ni Hao"
恭喜(gōng xǐ) = "Congratulations!"