Abstract: A stable and electroactive complex was formed by the reaction of Mn(Ⅱ) with o-phenanthroline (Mn∶Phen=1∶1) in an ammoniacal buffer medium of pH 9.5.Electrochemical behavior of the complex was studied by linear sweeping polarography and cyclic voltammetry,and a method for determination of Mn(Ⅱ) in tea was proposed.Conditions of the reaction medium,including the chioce of supporting electrolyte,concentration and pH of the buffer solution,and the type of sensitizing agent used,were tested and optimized.The electrochemical property of Mn(Ⅱ)-phen complex and mechanism of electrode reaction were studied.Under the optimized conditions,linear relationship between values of reductive peak current and concentration of Mn(Ⅱ) was obtained in the range of 6.3×10-8-8.0×10-7mol·L-1,with detection limit (3S/N) of 2.0×10-8mol·L-1.The proposed method was used in the analysis of tea sample,and the values of recovery found by standard addition method were in the range from 97.8% to 102.1%.