The purpose of this study was to evaluate the effectiveness of teaching training program in improving preceptors' knowledge of teaching feedback skills. The two-group experimental pretestposttest research design was adapted as a guide for this study. A stratified random sampling was adopted and 120 preceptors working in a medical center were recruited. 60 preceptors were assigned by random sampling to an experimental group in which a 3-hour teaching training program was adapted. 60 preceptors were assigned to a control group. Score of feedback skills was evaluated using a questionnaire with thirty-two items. Frequency, percentage, mean, SD, pair t-test, ANOVA, chi-square and GEE(Generalized Estimating Equation) were used to analyze the data. The results indicated that the experimental group had better improvement in teaching feedback knowledge than the control group during post-test. The average pre-test score was 19.28 points, and the average post-test score was 24.23 points for the experimental group; the average pre-test score was 21.55 points, and the average post-test score was 22.57 points for the control group. The improvement rate in experimental group was significantly higher than the control group in four dimensions of teaching feedback skills except for the dimension where opportunity was offered for trainee to express again. The results of this study show that the teaching training program could improve preceptors' knowledge of teaching feedback skills.