In order to further improve the management level of the National Earthquake Precursory Observation Networks of China,and evaluate rapidly and scientifically the quality of digital observation data on the basis of the current subject evaluation methods,the data quality evaluation method of the Earthquake Precursory Observation Networks are studied. A set of data quality evaluation index associated with data integrity,noise level,solid tidal effect,consistency and other aspects is obtained,and then the data quality evaluation method of the Earthquake Precursory Observation Networks is established with the help of standardized treatment and weighted average methods. Application results show data quality indexes of the evaluation method is relatively comprehensive and reasonable. The evaluation results are basically consistent with the actual situation of the networks data quality. The evaluation method has been used in the national regional precursory network appraisal work. The study lays a foundation for the rapid assessment and quality classification of the Earthquake Precursory Observation Networks.