The human speech organ consists of respiration system (lung, larynx), phonation system (vocal cord), articulation system (esophagus, pharynx, uvula, teeth, gingiva, palate, tongue, lip) and resonating system(oral cavity, nasal cavity, paranasal sinus). Because teeth are components of the articulation system, it has been reported that the persons with abnormally positioned teeth generally have abnormal occlusion and pronunciation. In this study, using /ㅅ(s)/, the most commonly mispronunced consonant in children with malocclusion, and the seven single vowels, /사(sa), 서($s\delta$), 소(so), 수(su), 스($s\omega$), 시(si), 세(se)/ and / ㅏ(a), ㅓ($\delta$), ㅗ(o), ㅜ(u), ㅡ($\omega$), 1(i), ㅔ(e)/ were recorded and analyzed using speech analysis program on computer by measuring formants and compared them for investigating the differences in pronunciation in children with Angle's class I occlusions and those with Angle's class II div.1 malocclusion. The result were as follows: 1. In the Angle's Class II div.1 group, there were no significant differences in F1 of all recorded sounds as compared with Angle's Class I group(p>0.05). 2. In the consonants, there were significant differences in F2 of /스($s\omega$)/ and F2/F1 ratio of /사(sa), 서($s\delta$), 시(si)/ between the two group(p<0.05). 3. In the vowels, there were significant differences F2/F1 ratio of /ㅓ($\delta$)/(p<0.05) and no significant differences in F2/F1 ratio between two group(p>0.05). 4. In the consonants, there were significant differences in F2 and F2/F1 ratio when succeeding vowels were high or low, and F2/F1 ratio when front in accordance with tongue position (p<0.05). 5. In the vowels, there were no significant differences in formant in accordance with tongue position(p>0.05)