The present invention discloses a shielding layer detection circuit and a transmission system. The shielding layer detection circuit includes a first resistive voltage division assembly, a second resistive voltage division assembly, a switch module, and a control module. The first resistive voltage division assembly is connected to a conductive shielding layer group to detect an electric leakage signal; the second resistive voltage division assembly has a first detection terminal connected to one terminal of the conductive shielding layer group and a second detection terminal connected to the other terminal of the conductive shielding layer group to detect a breakage signal; the switch module is connected to a power supply bus bar group to switch a transmission line connection/disconnection state of the power supply bus bar group.