A method for detecting branch fibers in a point-to-multipoint optical network, wherein the optical network comprises an optical splitting module and a plurality of branch fibers connected to different ports of the optical splitting module respectively, the method comprises: sending test signals to the branch fibers, wherein the test signals are respectively added, at the ports of the optical splitting module, with identification information for identifying the branch fibers connected to the ports; and receiving a reflection signal added with the identification information of a detected branch fiber, identifying the branch fiber corresponding to the reflection signal through detecting the identification information added to the reflection signal, and obtaining channel characteristics of the branch fiber according to the reflection signal, wherein each of the test signals is a wide-spectrum signal with wavelengths covering a preset spectrum section, and the identification information is added by the optical splitting module into the test signal by marking a frequency component corresponding to the branch fiber in the wide-spectrum signal, characterized in that the preset spectrum section is pre-defined with N frequency components specially for identifying the branch fibers, and each frequency component is defined as a binary code "1" or "0" depending on whether the frequency component is blocked; the N frequency components together define an N-bit binary code, and the N-bit binary code is used as the identification information of the branch fiber; and N-bit binary codes with different binary values correspond to different branch fibers respectively, the N frequency components of the test signal are selectively blocked at a port connected to the detected branch fiber in the optical splitting module, so that the test signal is added with an N-bit binary code of a code value corresponding to the detected branch fiber. sending test signals to the branch fibers, wherein the test signals are respectively added, at the ports of the optical splitting module, with identification information for identifying the branch fibers connected to the ports; and receiving a reflection signal added with the identification information of a detected branch fiber, identifying the branch fiber corresponding to the reflection signal through detecting the identification information added to the reflection signal, and obtaining channel characteristics of the branch fiber according to the reflection signal, wherein each of the test signals is a wide-spectrum signal with wavelengths covering a preset spectrum section, and the identification information is added by the optical splitting module into the test signal by marking a frequency component corresponding to the branch fiber in the wide-spectrum signal, characterized in that the preset spectrum section is pre-defined with N frequency components specially for identifying the branch fibers, and each frequency component is defined as a binary code "1" or "0" depending on whether the frequency component is blocked; the N frequency components together define an N-bit binary code, and the N-bit binary code is used as the identification information of the branch fiber; and N-bit binary codes with different binary values correspond to different branch fibers respectively, the N frequency components of the test signal are selectively blocked at a port connected to the detected branch fiber in the optical splitting module, so that the test signal is added with an N-bit binary code of a code value corresponding to the detected branch fiber.