The invention discloses a method for calculating the biological effect of an extra-high voltage power frequency electromagnetic field on the human body. The method is applied to an extra-high-voltage power frequency electromagnetic field design system, and comprises the steps that firstly, an electric transmission line model is built up; a human body model is built up; a heat energy arithmetic unit is built up; then the human body heat effect SAR values of different distances between the human body and the electromagnetic field are calculated; the different distances and the corresponding SAR values of the electromagnetic field on the human body are stored in a storage unit. According to the method for calculating the biological effect of the extra-high voltage power frequency electromagnetic field on the human body, an ADI-FDTD algorithm is adopted, the SAR values of the human body in the extra-high voltage power frequency electromagnetic field are calculated to determine the safety of the human body in the electromagnetic field, reference is provided for the electromagnetic environment of high voltage transmission, the biological effect of the human body and other problems, and theoretical foundations are provided for later laying of high-voltage power lines.