Abstract: Acid-cleaning technology of screen completion horizontal well is an effective measurement for cleaning the drilling fluid pollution in bore hole, and the acid-cleaning effect directly affects the well productivity. The early stage of acid-cleaning strings in Shengli oilfield has some deficiencies such as incompletely sealed well-washing valve, poor sealing effect of well washing packer and no drainage channels. Such problems directly caused poor acid-cleaning effect on horizontal wells. The acid-cleaning strings were specific modified and the sealing structure of washing valve was improved in this paper. And then well-cleaning packer equipped with flow path was developed. The new technology improves acid-cleaning performance and effectively enhances well productivity of screen completion horizontal wells.