With the constant growth of domestic taxis and taxi drivers, some problems arise in the taxi market as the supply outnumbers the demand. The problems include vicious competition, poor service quality, and even unlawful acts. In order to enhance the service quality of domestic taxis and to guide taxi companies in their operations, it is necessary to have the service quality of taxis evaluated. An effective evaluation system of the service quality of taxis should not only appraise the service quality of taxis in a fair and objective way, but also sheds 1ight on how taxi companies can improve their operation. To achieve such goals, a complete set of representative evaluation indices should be established. However, the massive number of evaluation indices that have been chosen extensively to meet all needs may lead to redundant appraising work and even a biased result, which is often caused by ignoring the significant relation among the indices. Therefore, this study aims to find out the relatedness levels among the preliminarily-chosen indices to service quality by means of the grey relation analysis model. Such relatedness levels will serve as the basis for analyzing the true relation among the indices. This study works on totally thirty-nine indices that are considered important by researchers, the authorities concernd, taxi companies, and consumers; these indices fall into four categories: vehicle equipment, service efficiency, management of the operation system, and records. The relatedness levels among these indices are computed by means of the grey relation analysis model. As a result, twenty-one indices are selected as the representative evaluation indices to the service quality of taxis, including seven indice concerning vehicle equipment, four concerning service efficiency, seven concerning management of the operation system, and three concerning records.