This study investigates the colorimetric reaction between dithizone and mercury in aqueous media which generate the orange Hg-dithizone complexes extracted by chloroform. Then combining with spectral analysis, the UV-vis spectral data of the complexes are obtained to build a forecast model. By means of the multiple linear regression model with SG smoothing method, RPD (Residual Predictive Deviation) of 3.2461 is reached with the detection limit of 0.1129 ug/L. This colorimetric method was found to be rapid, simple and sensitive for the detection of mercury in aqueous medium.