Abstract: Electrochemical behaviour of galena is studied in Ammonium dibutyldithiophosphate system, especially in high alkalinity media. It has been shown the product of galena with Ammonium dibutyldithiophosphate are element S and Pb(DTP) 2. Using sequential selective flotation of galena with DTP as the collector in high alkalinity,the suitable dosage of DTP was above 10^-3mol / L,which would affect the selectivity、increase the costing and threaten the environment. The above shortages can be solved by mixture with Diethyldithiocarbamate(DDTC). In addition,the suitable mass ratio was 1∶ 1 at pH = 11. 0,the commensurately dosage of DDTC was about 2. 2 × 10^-5mol / L,DTP was about 2. 5 × 10^-5mol / L,the optimum pulp potential was about 0. 2V.