Disclosed is an RS-485 circuit, which includes an RS-485 interface chip, a start detector, a control module and a counter. The RS-485 interface chip includes a data input terminal and an enable terminal, wherein the data input terminal is configured to receive a data signal, the enable terminal is configured to receive a start signal or a switching signal to make the RS-485 interface chip in a data transmitting state or a data receiving state. The start detector is configured to detect a first signal edge of the data signal to generate the start signal to the enable terminal. After detecting the first signal edge of the data signal, the control module outputs first counting information. The counter is configured to count based on the first counting information, and output the switching signal to the enable terminal when the counter expires.