The utility model provides a road traffic signal lamp, which mainly comprises two or three single lamps, two side plates, two circular plates and a supporting tube by which the single lamps can be connected in series. A dent which is matched with the outer circle of the supporting tube is arranged behind a shade body of a lamp shade of the single lamp. The utility model has the characteristics of modular design, convenient processing, convenient installation, novel structure, beautiful appearance, small volume, light weight, good sealing performance, free maintenance, mistaken judge avoidance, and enhanced traffic safety, and is capable of being combined into double lamps or three lamps. The utility model is a replacing product of traditional road traffic signal lamps.