The invention relates to the technical field of glass curtain wall self-cleaning, in particular to a building outer curtain wall mechanism with a self-cleaning device, which comprises a base, a glassbracket, a glass curtain wall, a water collection assembly, a water spraying assembly, a cleaning assembly and a detection assembly, and is characterized in that the water collection assembly comprises a liquid collection tank, a clear water storage tank and a water purification mechanism; the water spraying assembly comprises a water spraying head capable of spraying water to the outer surface ofthe glass curtain wall, the cleaning assembly comprises a lifting mechanism, a rotary driving mechanism, an attaching mechanism and a cleaning cylinder capable of cleaning the outer surface of the glass curtain wall, and the detection assembly comprises a camera. According to the building outer curtain wall mechanism with the self-cleaning device, glass stains can be automatically detected, the curtain wall can be automatically cleaned, the self-cleaning function is achieved, rainwater and washing water can be collected and utilized, purified water is used for self-cleaning operation of the curtain wall, sewage is collected, the utilization rate of water resources is increased, and the lighting effect of the glass curtain wall is improved.