The invention discloses a cooperatively preprocessing method of a solid waste incineration flying ash cement kiln of a returned effluent in the technical field of solid waste treatment and disposition. The method comprises four stages of flying ash washing and dechlorinating, washings processing, washed ash dehydrating and calcining in the kiln, wherein, at the stage of flying ash washing and dechlorinating, heavy metals washed out in the washing process are chelated, flocculated and settled, then is filtered and pressed together with the washed ash, and then is put into the kiln. Neutralization and heavy metal sedimentation are carried out on an eluate so that the washings can be discharged after reaching standards. When used for processing flying ash, the method not only can save the raw materials in the cement industry, but also can effectively fixing heavy metals, completely burn dioxin, safely, economically and fast dispose flying ash and greatly improve the environmental, economic and social benefits. With the method, occupied area, water and investment are saved, the operation is reliable, the washed ash and the washings are processed with stable effect, and no secondary pollutant is caused.