The invention discloses a side slope monitoring device which comprises a pile body, a rainfall monitoring assembly, a soil monitoring assembly and a wind speed measuring piece. The rainfall monitoring assembly comprises a reservoir and a water pressure sensing piece. Rainfall data is obtained through the reservoir designed at the top, wind speed data is obtained through the wind speed measuring piece, soil data is obtained through the soil monitoring assembly, when the data change reaches the risk of landslide or debris flow, information is sent to related departments through the information processing system, then an alarm lamp is used for giving an alarm, and an irreparable disaster loss is avoided; and moreover, through the rotationally arranged reservoir, when the water in the reservoir is excessive, the reservoir is automatically overturned, accumulated water in the reservoir is poured out, the influence on the acquisition of rainfall data is avoided, meanwhile, the arrangement of a valve or other structures for discharging the water is also avoided, and the practicability is good.