The invention relates to an adjustable-length sampled data trigger method, and belongs to the technical field of data processing. The method comprises the following steps: sampled data are traversed and compared with a set valid data capture threshold in a traversing process; and whether the sampled data is larger than the set valid data capture threshold is determined, and if the sampled data is larger than the set valid data capture threshold, the sampled data is intercepted and stored according to a set interception length. Therefore, valid data in a continuous data acquisition process is captured, a large quantity of invalid data and fewer valid data in the continuous data acquisition process are separated and stored, invalid sampled data are reduced to the greatest extent, the storage space is saved, follow-up analysis of the stored data is facilitated, and besides, the valid data capture threshold and the interception length are dynamically adjustable under different conditions, so that different application requirements are met, and the method has wide application field and prospect.