Abstract: In this paper, another new sensitized colored multicomponent coordination compound in the system of "Chromium(Ⅲ)——Eriochrome cyanineR——Alkyl dimethy laminoacelic acid" has been developed. The optimum conditions for the formation of the coordination compound in this system have been studied. It will not be decomposed by various masking agents such as EDTA, CyDTA, citric acid, tartaric acid etc; while in that case, almost all the colored coordination compounds formed by other ions will be decomposecompletely. This inert character of this multicomponent coordination compound and its utilization in improving the analytical selectivity have been discussed. In the coexistence of various foreign ions, the direct determination of chromium has shown a satisfactory reproducibility. It was also proved as our former report that the sensitizer cetyl dimethylaminoacetic acid(CDMAA) or tetradecyl dimethylaminoacetic acid(TDMAA) is more suitable to be used in the spectro-photometric determination of microamount of chromium with high sensitivity. When CDMAA and TDMAA are used as sensitizer in this system, the molar absorptivity are 1.14×10⁵ and 1.22×10⁵ respectively. From the results of determination in some synthetic and actual samples, it showed feasible to use this system in the determination of low chromium in steels and microamount of chromium in the waste water from elctroplating or other industries.