The invention discloses a method and a system capable of spraying dilute sludge into a kiln. According to the method, dilute sludge is sprayed into a decomposition furnace in a mist manner, stink produced by the dilute sludge is introduced into the decomposition furnace, and the dilute sludge is subjected to impurity removal before being sprayed. The system comprises the decomposition furnace communicated with a cement kiln, a sludge sprayer is arranged at a feeding port of the decomposition furnace, the feeding port of the sludge sprayer is communicated with a discharging port of a sludge bin through a sludge delivery pump, and a high-pressure air inlet of the sludge sprayer is communicated with a high-pressure air source. The drying process of the dilute sludge is simple, the investment is low, nitrogen oxide emission can be reduced significantly, the drying time is short, the dilute sludge disposal efficiency is high, the floc structure formed by spraying the dilute sludge into the kiln directly is avoided, decrease of the local temperature of the cement kiln and deterioration of the combustion working condition are prevented, and the yield and quality of clinker can be guaranteed. The atomization effect on the dilute sludge is good, the service life of the sludge sprayer can be prolonged, and installation is simple and convenient.