The invention discloses an application of DTT (di-thiothreitol) in improving CELI-family enzyme activity. The concentration of DTT in an enzyme digestion buffer solution ranges from 0.01mM to 10mM. The method is more flexible, and detection sensitivity of CELI enzyme and CELII enzyme final concentration of the DTT can be improved by final concentration of the DTT within the range of 0.01mM to 10mM. For detection of low-abundant unknown mutants, good detection effect on certain cancer genes is good, a TILLING technology platform has specifically obvious advantages in detecting induced groups, PCR (polymerase chain reaction) purification procedure is simplified, and detection resolution is correspondingly improved.