The invention relates to an FPGA-based A/D real-time fault diagnosing method. The method is characterized in that an A/D chip is connected with a CPU through an FPGA; the FPGA performs A/D fault information diagnosing while acquiring the A/D data and records the A/D fault; the A/D fault information and the A/D data are processed to form a message to be sent to the CPU at the opposite end. With the adoption of the method, the shortage that the current CPU software cannot effectively detect SV data on real time can be overcome; the FPGA-based A/D real-time fault diagnosing method is high in real-time performance, high in expansibility and portability; the SV data can be detected at the sampling source end; the problem of the A/D chip suffering from a fault can be positioned well.