The invention provides a water bloom 
early warning system and method based on combination of on-line monitoring and image recognition. The 
system comprises an on-line acquisition device and a background early warning platform. The online acquisition device is suspended in a to-be-detected 
water body and comprises a physicochemical index detection template and an 
image acquisition module, the physicochemical index detection module is used for acquiring 
water quality physicochemical indexes of the to-be-detected 
water body, and the 
image acquisition module is used for acquiring images in the to-be-detected 
water body; and the background early warning platform compares each 
water quality physicochemical index with a corresponding set threshold, determines the 
eutrophication degree of the to-be-detected water body, evaluates the water bloom 
outbreak risk level in combination with the color similarity between the image in the water and a reference old water image, and performs water bloom early warning according to the 
outbreak risk level. Through automatic on-line monitoring of 
water quality physicochemical indexes and combination with an image recognition technology, while accurate water bloom prediction is achieved, the labor and 
time cost is reduced, and the method can be widely applied to 
water source monitoring places such as rivers, lakes and reservoirs and has high 
actual use value.