A dual-line protocol read-write control chip, system and method. Said chip comprises: two front-stage ports, two rear-stage ports, a protocol decoding module, a data forwarding module, a read-back control module, a display control module, a gradient control module and an instruction control module; data is input to a chip based on a dual-line transmission protocol; after the chip decodes the data, the instruction control module controls a corresponding module according to the decoded instruction data; the data forwarding module forwards the data to a next-stage chip; in a read-back mode, the input and output ports of the chip are interchanged, so that corresponding state parameters can be read back from the chip, and then the working state of the chip is adjusted, and the gray scale of an LED light can be directly controlled according to the decoded gray scale data.