The purpose of this study was to find the relationship between Juvenile Delinquents´ Criminal behavior and Psychological characteristics. We set up 5 hypotheses which were tested with Intelligence and Personality tests. The sample of subjects was chosen from Hsin-chu Juvenile Prison and Tau-yuen Juvenile Reformatory according to the criminal behavior, such as stealing, robbing, murdering and cheating. The total number of subjects is 239, 96 of them are thieves, 61 are robbers, 72 are murderers and 10 cheaters. The results of these tests can be stated as follows: (1) Thieves´ IQ is lower than those of murders´. (2) Cheaters´ IQ is higher than those of thieves´. (3) Aggression of murders is not stronger than those of thieves and cheaters. (4) Robbers have more depressive disposition than thieves, murderers and cheaters do. (5) Thieves have more social-extraverssive disposition than robbers and murders do. From the above results, We have found that there are two facts which do not accord with our hypotheses, namely, the thieves are less intelligent than murders, and murders´ aggression is not stronger than thieves´ and cheaters´. Therefore, further investigation is needed in these aspects.