In 1982,Fu presented his work on realizing Maxwell’s demon.Fu declared that a perpetualcurrent was obtained in his device.This means that a new machine of the second kind of perpetualmotion has been invented.In this paper,the author gives a detail analysis on Fu’s work,and thefollowing conclusion has been obtained:(1)In Fu’s experiment,the object centrolled by the magneticfield was electrons in mass,not in individuality.The magnetic field did not separate electronsindividually into a high-speed group nor a low-speed group.For this reason,it was not a“demon”.Thewhole process in the experiment was a mass-flowing process of an enormous amount of small particles.This must belong to the area of thermodynamics.(2)The current flowing in Fu’s device isactually the initial velocity current of a vacuum diode.(3)The initial velocity current is,in turn,a modified form of Thomson thermo-electric effect,which requires a hot tank and a cold tank,obeyingthe second law of thermodynamics.(4)The role of action of the magnetic field is to control electronsin mass,causing a weak rectification in the device.The current should vanish if there has no suchaction,because the initial velocity electrons should eliminate by each other.(5)Fu’s approach wasnot a proper approach to realize the Maxwell’s hypothesis. In 1982, Fu presented his work for realizing Maxwell’s demon.Fu declared that a perpetualcurrent was obtained in his device. This means that a new machine of the second kind of perpetualmotion has been invented. In this paper, the author gives a detail analysis on Fu’s work, and the closing conclusion has been obtained: (1) In Fu’s experiment, the object centrolled by the magnetic field was electrons in mass, not in individuality. Magnetic field did not separate electrons individually into a high-speed group nor a low-speed thewhole process in the experiment was a mass-flowing process of an enormous amount of small particles. This must belong to the area of ​​thermodynamics. (2) The current flowing in Fu’s device isactually the initial velocity current of a vacuum diode. (3) The initial velocity current is, in turn, a modified form of Thomson thermo-electric effect, which requires a hot tank and a cold tank, obeying the second law of thermodynamics. ( 4) The role of action of the magnetic field is to control electronsin mass, causing a weak rectification in the device.The current should vanish if there has no suchaction, because the initial velocity electrons should eliminate by each other. (5) Fu’s approach wasnot a proper approach to realize the Maxwell’s hypothesis.