A nonaqueous capillary electrophoresis (NACE) method was developed for simultaneous assay of three bioactive components (1: cryptotanshinone; 2: tanshinone IIA, and 3: tanshinone I) in Radix Salviae miltiorrhizae and in its herbal preparations for the first time. After optimization of separation conditions, a buffer of 250 mmol L(-1) ammonium acetate containing 30% acetonitrile and 1.0% acetic acid (V:V) in methanol was selected for separating the three analytes, but baseline separation of tanshinon I and tanshinone IIA was not obtained. Therefore second-order derivative electropherograms were applied for resolving overlapping peaks. Regression equations revealed good linear relationships (correlation coefficients 0.9943-0.9991) between peak heights in second-order derivative electropherograms and concentrations of the three analytes. The relative standard deviations (RSD) of the migration times and the peak height of the three constituents were in the range of 0.81 -0.88% and 0.34-1.13% (intra-day), 1.57-1.86% and 3.05-5.52% (inter-day), respectively. The recoveries of three constituents ranged from 90.2 to 108.5%. The results indicated that baseline separation of the analytes was sometimes hard to obtain and second-order derivative electropherograms were applicable for the resolving and analysis of overlapping peaks.