The utility model discloses a multi-channel circuit weak voltage signal acquiring device for a logging instrument, which comprises the components of a parallelly connected multi-channel circuit which comprises a fixed-gain channel circuit and a programmable-gain channel circuit; an analog-to-digital converter drive ADC which is correspondingly connected with the multi-channel circuit, wherein the analog-to-digital converter drive is parallelly connected with an analog-to-digital converter AD; an isolating ISO chip which is connected with the analog-to-digital converter; and a field programmable gate array FPGA chip which is connected with the isolating chip. According to the multi-channel circuit weak voltage signal acquiring device, hardware difficulty is reduced and furthermore accurate signal acquisition is realized.