The invention relates to a signal triggering method and device based on periodic signal transient variable quantity. The signal triggering method comprises the following steps that S1, a periodic signal is collected, and transient disturbance quantity is obtained according to the periodic signal; S2, whether the absolute value of the transient disturbance quantity at each collection point is greater than a first set value or not is determined, if yes, the step S3 is performed, and if no, the step S1 is returned; S3, whether continuous collection time of the transient disturbance quantity withthe absolute value greater than the first set value is greater than or equal to a second set value or not is determined, if yes, the step S4 is performed, and if no, the step S1 is returned; and S4, atrigger signal is generated. Compared with the prior art, the signal triggering method and device based on the periodic signal transient variable quantity have the advantages of high in sensitivity,and wide in application range.