The purpose of this study is to investigate the acquisition of language through the mistake of predicate by Korean children of 36-83 months. In children`s speech, we find morphological errors; the incorrect insertion of epenthesis vowel ``으``, the reconstruction of stems, inflection, an affix, the use of unstandard stems and the adding of unnecessary sound etc. Results show that (1) the most important period is 60 months of age. Until 60 months of age the error of inflection increase, but from that time on, the errors decrease considerably. (2) the incorrect insertion of epenthesis vowel ``으`` was observed in different environments than adults. (3) the children overall reconstruct irregular verbs more often than regular verbs. (4) the children tend to substitute the variants which precede the universal ending``-아/어``morpheme. (5) an affix is replaced by ``-어지다``. These finding are that young children consider the word forms that they are frequently exposed to as a basic form, and tend to change irregular paradigm to regular one.