The invention discloses scaling powder for no-clean lead-free low-silver welding paste. The scaling powder comprises, by weight percentage, 3-13% of active agent, 0.2-1.5% of surface active agent, 0.2-3.0% of emulgator, 3.0-10.0% of thixotropic agent, 3-8% of film-forming agent, 0.1-1% of antioxidant, 0.1-0.5% of corrosion inhibitor and the rest of solvent. The active agent is composed of four or five components in succinic acid, oxalic acid, salicylic acid, glutaric acid, citric acid, adipic acid, lactic acid, benzoic acid, malic acid and triethanolamine. The scaling powder for the no-clean lead-free low silver welding paste does not contain halogen, the corrosion to a circuit board is greatly lowered, the printing quality of the welding paste is good without bridging or turned-down edges, a welding point is good in forming after returning, the brazing connecting defect is greatly lowered, the residue is small without solder balls, the cleaning is not needed, the welding paste is directly used for assembling, the Sn-0.45 Ag-0.68 Cu or Sn-0.3 Ag-0.7 Cu low silver welding paste manufactured by using the scaling powder does not contain the halogen and rosin, the organic chemistry smoke is small, and the pollution to the environment is small.