The invention discloses a high-precision real-time time source generation method for B code synchronization, which is characterized in that the method comprises the following steps: starting a program, waiting for the B code signal to start; finding the signal head of the B code signal; recording a second synchronization signal and clearing the counter; performing B code decoding on a time more than a second by a B code decoding module; when there is no B code signal outside, counting the time less than a second by the clock management module; combining the time more than a second and the time less than a second to obtain the date and time value of the current decoding. The invention adopts B code decoding to decode a time more than a second, adopts digital crystal oscillator pulse mode to calculate a time less than seconds, and obtains accurate time by combining less than seconds time and more than seconds time. Therefore, the method can be used for timestamping, uniform packet distribution or host reading time.