12. The language learning method according to claim 11 , wherein the step of extracting the pronunciation feature of each of the training data comprises: collecting a plurality of training sentences; performing a phonetic segmentation operation on the training sentences to obtain a plurality of pronunciation units of the training sentences; and obtaining the training data from the pronunciation units.
20. The language learning method according to claim 12 further comprising: grouping the training data into a plurality of training data groups according to combinations of each pronunciation unit and the previous pronunciation unit in the training sentences; and generating the assessment decision trees according to the training data groups, wherein each of the assessment decision trees is corresponding to one of the training data groups.