It's always difficult in technology to eliminate power interference of 50 Hz in Brainwave Data Acquisition System .Though traditional ways to eliminate it can also gain some effects, they have drawbacks such as high cost and low currency at all time. The use of trap filter of 50 Hz may solve the question radically. Through the authors' repetitious experimentation, it is proved that trap filter of VCVS not only eliminate power interference of 50 Hz farthest but also have merits of simple circuit structure, convenient coupling and upper reliability. The authors offer collected brainwave in strong power interference environment. It may be seen that it is very clear and clean. Because power interference of (50 Hz) exists in almost all Data Acquisition System, this type of trap filter possesses better currency, it is expected to win extensive application in medical apparatus of measurement of other biological electricity signals and industrial observation and control system.