Carrying out data transmission based on signal line and ground wire between transmitter and receiver, the method in serial comm. includes parts and sequences: when not carrying comm. between transmitter and receiver, maintaining signal line at first level; transmitter sets signal line to second level, and after maintains prearranged time lengths of start bit, data 1, or 0, restores level to first level to indicate starting comm. data 1, or 0. There are different time lengths among start bit, data 1, or 0. The disclosed interface circuit includes interface circuits of transmitter and receiver. Signal lines and ground wire are connected between interface circuits. When transmitting end has no input or is in high level, the receiving end is in high level; when low level is inputted to the transmitting end, the receiving end is at low level. The invention enhances interference-killing feature for serial comm. without need of transmitter and receiver of possessing same reference clock.