Abstract: A proper method is proposed in this paper to eliminate the additional electric current by electrons with high energy in the Langmuir V-I characteristic curve when plasma consists of two groups of electrons at different temperatures and under the condition that T_e>>T_i. The study showed that after this correction the result of electron temperature measured is more reasonable. Another method to obtain electron temperature using Ion-Acoustic Wave speed was also studied in this paper. The ion-acoustic wave in this experiment was excited by either tone-burst test wave method or by CW test wave method. The comparison of the electron temperature of the plasma using the above correction method with that calculated from ion-acoustic wave (IAW) speed shows that the average error of electron temperatures from IAW speed △T_e (about 0.1 eV) is much smaller than that from Langmuir V-I characteristic curve (about 0.44eV, after the above mentioned correction). It can be concluded that to make an additional correction is a good way to raise the accuracy of electron temperature measurement while using IAW method seems better in certain cases.