Abstract   Background:   Puberty is of high importance and physical, psychological and social changes occurs in the period.This period has great impact onadult life and also the futureand given rise to conflict between parents and children and the role of parents, especially mothers in this period due to build healthy families in our country's founding figures of children, this study aimed to evaluate the knowledge, attitude and behavior about psychological changes during puberty and its association with the relationships between girls and their mothers were studied.   Method:   In this descriptive study , 161highschool studentsin the first period(n = 74 in seventh gradeand n = 87 in thirdgrade ) in Zanjan city, selected by the M ulti -stage samplingof the sixhighschool in the first period(secondary school) enrolledin this study. Bycollectingdata onknowledge,attitude and practice of questionnairecontaining18 knowledge questionsand20 attitude itemsand20 questionsaboutthefunctional, andby collectingdata onrelationship betweenmother anddaughter of a standard questionnaire PCRS containing 24 questionsto assess child-parent relationship , but studentscompleted.Datacollectedby SPSS-18 softwareandANOVAtests,regression and correlation , and thesignificance levelα = 0.05 wasanalyzed .   Results :   The mean age of maternalage38.17±5.36 years and the average age of students was13.19 ±0.72 years. The mean scores of mothers' knowledge about nonphysical changes of puberty 9.58± 3.48 out of 18 score and the mean attitude score 64.81± 8.84 out of 100 score and the mean score of their practice, 57.4 ± 5.82 out of 80score was thatthe score of the three were in the moderate range. Average score of mother-child relationship during puberty was 20/44 out of 28 score that was in the range of a moderate relationship.Mother-child relationship and the attitude and practice were correlated.mothers' attitude and practice were correlated.   Conclusion:   Many of mothershad knowledgeabout thematurity ofmiddle and lowerlevel and more of them had positiveattitude and a moderateyield in practice andmaintain goodrelationshipwithherteenage childrenwere.Relationship between thechildand the motherwith mother' attitude and practicecorrelated . Itis recommended for mothersto raise awarenessand createa positive attitudeand good performanceintheprovision ofappropriatetraining programs willbe affective .   Key words: Adolescent, Knowledge,attitude, practice and relationship.