Multi-data-source synchronous output calibration method and system independent of external clock

The invention discloses a multi-data-source synchronous output calibration method and system independent of an external clock, and relates to the field of intelligent substation equipment testing. According to the technical scheme, the method specifically comprises the steps that the theoretical clock number and the actual clock number of a crystal oscillator in a standard time step length of a first moment are obtained, the standard time step length is determined based on a standard clock source, and the theoretical clock number is obtained through calculation according to the frequency of the crystal oscillator and the standard time step length; the actual clock number is obtained by actually measuring the clock period of the crystal oscillator within the standard time step length; and calculating a jitter error based on the theoretical clock number and the actual clock number, compensating a clock period in a standard time step length of a second moment based on the jitter error to complete clock calibrati