Abstract: This paper studies the ionospheric TEC calculated f rom the GPS data received in Wuhan,Beijing,Wulumuqi stations during the flare burst on July 14,2000.The TEC in the ionosphere is calculated.The method for calculating TEC enhancement only caused by the solar flare is presented.The calculating results indicate that the polynomial fitting method can effectively calculate TEC enhancement.The fitting period of time should be chosen by the actual TEC curve.