Abstract: Because of its fatal imperfections in the logical procedure, the widely-accepted analysis in the form of phasor method applied to obtain the en-oscillating condition and the stabilizing condition for feedback oscillator prove wrong. In the paper, a general en-oscillating criterion is brought forward for the first time, and by means of this criterion, two concrete en-oscillating condition in the form of phasor method are logically deduced, which are reasonably practicable. In the end, the stabilizing condition for oscillator is sentenced to be nothing.