A filament simulation circuit for LED tube, comprising: two filament simulation parts respectively disposed on two terminals of a tube to receive a current from an electronic ballast, each filament simulation part including two sub-filament simulation parts, each sub-filament simulation part including a first resistor, a capacitor and a inductor, wherein each sub-filament simulation part is divided into: a first part; and a second part connected in series to the first part, the second part having a parallel connection structure; wherein an impedance of the sub-filament simulation part in a pre-heated stage is greater than that in an operating stage.