The invention relates to a method for realizing the self-adapting conversion of an X-ray nonstandard video digital code by using an FPGA (Field Programmable Gate Array). The step of calculating a parameter of an X-ray nonstandard analog video signal concretely comprises the following steps of: (2a) controlling a synchronous phaselocked loop by using an FPGA chip to provide a reference clock with an F frequency, sampling an input video signal with the reference clock by using an analog-to-digital converter and inputting digital data to the FPGA chip; and (2b) calculating the digital data according to the obtained field synchronous signal combining with a reference clock signal with the F frequency to obtain a parameter of an input video. The invention concretely discloses means for calculating the parameter of the X-ray nonstandard analog video signal, a method for calculating an actual sampling frequency and a method for reading a valid signal. The defect in the prior art is overcome and the method for converting the X-ray nonstandard analog video into a standard video is perfected.