Different methods are used for teachers' evaluation; one of these methods is using students comment. Despite development of educational evaluation by students, it doesn't exist a positive attitude for this process because of different factors affection. This study was conducted to investigate factors affecting teachers' evaluation from students' viewpoint and its relation with educational achievement. In this descriptive analytical study, 554 participants studying at Kermanshah University of Medical Sciences in 2013 were selected using simple random sampling. Self-administered questionnaire was used to collect data which consisted of 37 questions with Likert scale ranging from very high to very low rating of 1 to 5, respectively. Questions included five areas of teaching skills (7 items), teacher's personality characteristics (16 items), students’ personality characteristics and attitudes (6 items), physical characteristics and time course (4 items), and evaluation process at university (4 items). Content validity of the questionnaire determined by respective experts, and its reliability was calculated 0.73 through chronbach's alpha test. Affecting factors on teaching skills and students' personality fields with teachers evaluation and educational achievement were not significantly related. Although, result showed that students' personal characteristics and attitude besides time of course presentation were factors that had significant relationship with students educational achievement in their teachers evaluation (p=0.04, p=0.37). Regarding no significant relationship of teaching skills and teachers' personal characteristics with students educational achievement, it seems that students' scientific level in teachers evaluation is ineffective factor, therefore, factors affecting teachers evaluation can be reduced by altering forms and educational curriculum.