The invention relates to a CBTC signal system DCS fault diagnosis and early warning analysis method. The method comprises the steps that (1) real-time monitoring and automatic analysis of train-groundwireless field strength are carried out, and a wireless field strength monitoring train is dynamically selected and enabled according to a train operation plan; (2) wireless field strength monitoringand indoor and outdoor equipment status are combined to carry out DCS equipment fault diagnosis and early warning to accurately locate the fault location and causes; (3) based on long-term wireless field strength analog monitoring information, wireless field strength long-term trend tracking and trend early warning are realized; (4) capturing analysis and over-limit grading early warning are carried out on abnormal fluctuations and abrupt changes of DCS equipment performance and key operating parameters; and (5) maintenance suggestions and handling instructions based on a fault schematic diagram are provided for each type of DCS fault and early warning. Compared with the prior art, the method provided by the invention has the advantages of real-time automatic monitoring and analysis of DCS train-ground wireless field strength and the like.