The purpose of this study is to explore the effects of teacher's traits, classroom management style on teacher's pet phenomenon. Subjects, including 424 middle and primary teachers, were randomly drawing from schools in Taiwan. They were investigated by Basic Information Investigation Scale, Classroom Management Style Scale, and Teacher' Authority Scale. Statistics methods of Frequency. X2, t-test, three-ways ANOVA and Discriminant Analysis were used to analyze related data getting from subjects. The main finding are mentioned as following: 1.The "Teacher's Pet Phenomenon" existed in the classroom in Taiwan. The popular style of "Teacher's Pet Phenomenon" was exclusive-pet classroom. 2.There was different concerning "Teacher's Pet Phenomenon" between middle and primary school teachers. 3.No differences of numbers of teacher's pets existed between middle and primary school teachers. 4.Generally, students who could be helpful to deal with classroom affairs for teachers and taking responsibility were beloved by teachers than others. 5.Variables of gender, service years, work satisfaction of teachers affected classroom management style. 6.Three main variables could predict significantly types of teacher's pets tested by Discriminat Analysis. Finally, some suggestions were made for educators and future study according to findings.