A hybrid optical direct-current measurement system in-place converter comprises an optical current transducer, an electric energy and communication control signal separation circuit, an isolation circuit, a DC-DC switching circuit, a clock extraction module, a low-voltage judgment module, a simulation sampling module, an AD conversion module, a CPLD module, and a laser diode. An input of the electric energy and communication control signal separation circuit is connected with the optical current transducer, and an output of the electric energy and communication control signal separation circuit is respectively connected with the isolation circuit, the clock extraction module and the low-voltage judgment module. The input of the DC-DC switching circuit is connected with the isolation circuit, and the output of the DC-DC switching circuit is respectively connected with the low-voltage judgment module, the simulation sampling module, the AD conversion module, the CPLD module and the laser diode. The input of the simulation sampling module is connected with a low voltage side of a mutual inductor, and the output of the simulation sampling module is connected with the AD conversion module. The input of the CPLD module is respectively connected with the clock extraction module, the low-voltage judgment module and the AD conversion module, and the output of the CPLD module is connected with the laser diode. The hybrid optical direct-current measurement system in-place converter has the advantages of low power consumption, high accuracy, high reliability, low cost, and seamless joint with the present system.