[en] Based on Biot-Savart law, through learning the internal EAST plasma current state of motion, establishing the mathematical model of magnetic field inside EAST, simulating and analyzing the experimental data by Matlab, the model is analyzed and verified. Through error analysis, the model is improved, and studies show that improved model fit well with the experimental data, the error is small. Meanwhile related research and conclusions have some significance for measuring the magnetic field of tokamak vacuum chamber, it provides the theoretical basis for MEMS magnetic sensor on electromagnetic measurement system of superconducting tokamak. (authors)