Abstract: Separation and inspection of nanoparticles of TiO2 and Al2O3 in a mixed suspension were performed simultaneously by capillary electrophoresis with non-contact conductivity detection.Various factors,including kinds and concentration of buffer solutions and pH of solution influential to the efficiency of separation,were scrutinized and effects of excitation frequency and alternating current excitation voltage on the signal to noise ratio of measuring signal were also studied.Nanoparticles of TiO2 and Al2O3 of different grain size in a suspension were completely separated within 8 min under the following optimized conditions: ① buffer solution: 5 mmol·L-1 Na2CO3 and NaHCO3 mixed solution of pH 10.5;② separation voltage: 20 kV;③ sample introduction at 20 kV for 6 s;④ excitation frequency: 460 kHz;⑤ AC excitation voltage: 4 V,giving highest value of S/N ratio.