A long-distance box for a Passive Optical Networks, PON, system where different PON systems coexist, wherein the long-distance box comprises a first long-distance amplification box and a second long-distance amplification box and a first wavelength division multiplexing filter and a second wavelength division multiplexing filter; the system in which the different PON systems coexist comprise a first PON system and a second PON system; the long-distance box is configured to process uplink/downlink lights from the PON systems, which passes through an optical path in which the long-distance box is located, wherein the first long-distance amplification box is located in a first optical path and the second long-distance amplification box is located in a second optical path; the first wavelength division multiplexing filter is configured to split the downlink lights and couple the uplink lights from different PON systems, the uplink/downlink light from the first PON system is transmitted through the first optical path and amplified by the first long-distance amplification box, and the uplink/downlink light from the second PON system is transmitted through the second optical path and amplified by the second long-distance amplification box; and the uplink lights transmitted through the first optical path and the second optical path are coupled to a trunk optical fiber through the first wavelength division multiplexing filter; and the second wavelength division multiplexing filter is configured to split the uplink lights and couple the downlink lights from different PON systems, the uplink/downlink light from the first PON system is transmitted through the first optical path and amplified by the first long-distance amplification box, and the uplink/downlink light from the second PON system is transmitted through the second optical path and amplified by the second long-distance amplification box; and the downlink lights transmitted through the first optical path and the second optical path are coupled to the trunk optical fiber through the second wavelength division multiplexing filter, wherein the wavelength division multiplexing filters consists of filtering sheets with double windows and each wavelength division filter comprising an interface R, an interface P and an interface C; the uplink/downlink light from the first PON system is reflected and input/output through the interfaces R, the uplink/downlink light from the second PON system is transmitted and input/output through the interfaces P; and the interfaces C are connected with the trunk optical fiber; the interface C of the first wavelength division multiplexing filter is connected with the trunk optical fiber at an Optical Line Terminal, OLT, side, the interface R of the first wavelength division multiplexing filter is connected with one end of the first long-distance amplification box in the first optical path, and the interface P of the first wavelength division multiplexing filter is connected with one end of the second long-distance amplification box in the second optical path; the interface C of the second wavelength division multiplexing filter is connected with the trunk optical fiber at an Optical Network Unit, ONU, side, the interface R of the second wavelength division multiplexing filter is connected with the other end of the first long-distance amplification box in the first optical path, and the interface P of the second wavelength division multiplexing filter is connected with the other end of the second long-distance amplification box in the second optical path.