Magnetic field and electromagnetic wave are harmful to human being or not? Some mobile phone industries emphasize the relatively low electromagnetic wave. In fact, there are many invisible electromagnetic waves in our living environment, and the electromagnetic radiation of mobile phone is one kind of electromagnetic wave. In order to protect the personal security, our government followed ICNIRP and announced in 1998 the radiation environment proposing value. Our research use questionnaire and real measure methods to analyze the data. The results show that the best time to answer mobile phone is exceeding ten seconds or using earphone.