The embodiment of the invention relates to an ion migration tube signal extracting circuit and method as well as an ion migration detector, which relate to the technical field of substance detection and solve the technical problem of larger designing and manufacturing difficulty of a leading-out circuit of pulsating voltage on a faraday's disc in the prior art. The ion migration tube signal extracting circuit comprises a direct current isolating and alternating current conducting module, wherein the direct current isolating and alternating current conducting module is used for removing direct current voltage in the voltage led out from the faraday's disc via a signal leading-in end and used for outputting pulsating voltage in the voltage, which is led out by the signal leading-in end from the faraday's disc, from a signal leading-out end. The ion migration detector comprises an ion migration tube signal extracting circuit provided by the invention. The ion migration tube signal extracting method comprises the following steps of: leading out the voltage on the faraday's disc in an ion migration tube; removing direct current voltage in the voltage led out from the faraday's disc; and outputting the pulsating voltage in the voltage led out from the faraday's disc. The ion migration tube signal extracting circuit and method as well as the ion migration detector, provided by the invention, are used for leading out the pulsating voltage on the faraday's disc.