The invention relates to an automatic rainfall intensity warning device with high-slope-stability monitoring. The automatic rainfall intensity warning device comprises a rainwater harvesting system, a normal working circuit and a monitoring and early-warning circuit. The rainwater harvesting system includes an outdoor organic glass jar, an indoor organic glass jar, and a water pipe. The bottom of the outdoor organic glass jar is connected with the indoor organic glass jar by the water pipe. The normal working circuit consists of a first indicator lamp and a power supply that are connected in series by a lead to form a loop. The monitoring and early-warning circuit consists of a power supply, an electromagnetic relay, an alarm horn, a second indicator light, a first copper ball and a second copper ball, wherein the first copper ball, the power supply, the electromagnetic relay, the alarm horn, the second indicator light, and the second copper ball are connected by wires successively; the first copper ball is arranged at the bottom of the indoor organic glass jar; and the second copper ball is arranged in the middle of the indoor organic glass jar. According to the invention, connection or disconnection of the circuit is triggered based on a rainwater level situation and rainfall intensity warning information is sent out, so that the administrator enhances slope monitoring timely and takes treatment measures in advance.