As voice technology receives wide application in our daily lives, Question-and-answer service is taking shape in the research of humanoid robot. This paper designs a humanoid robot Voice Q & A system based on cloud. After the robot collects voice signals, it would first process the signal to understand the question, and then searches the Internet for the best answers and tell it to the user with voice. In this system, dominant cloud technology is introduced and robot technology, speech recognition technology and Internet searching technologies are combined, providing people with a new way of human-computer interaction through natural language. Results show that with the application of cloud technology, the efficiency of speech recognition and the accuracy of answers have been enhanced substantially.