The invention discloses a test data compression method based on a dichotomy symmetric folding technology. Vectors in a test set are arranged according to the degressive sequence of the number of determined bits. The first vector in the sequenced test set is selected as a seed, and a folding set is generated. The vectors in the test set are compared with vectors in the folding set, if Cj is the bit of the determined bit, the value of the bit, corresponding to Cj in position, in Vi is the unrelated bit or the same determined bit, or if the value in Cj is the bit of the unrelated bit, the value of the bit, corresponding to Cj in position, in Vi is the unrelated bit; the vector VI is deleted from the test set. The process is repeatedly carried out till the test set is null, and the obtained seed set S is the corresponding result of the test data T through compression. Compared with the prior art, the test data compression method has the following advantages that the non-invasive type test data compression method is adopted, a tested circuit structure is not changed, the structure of a scan chain in the circuit is not changed, the seed set is used for covering the whole test set, the compression rate is increased, the testing power consumption is reduced, and the test application time is shortened.