This topic "The Benefit of Using Communicative Language Teaching (CLT) in English Speaking Skill Classes: A case study at Department of English Language, Faculty of Letters, National University of Laos " is quantitative experimental research. The purpose of the study was to observe the differences in students' speaking scores before and after using CLT in experimental group and traditional teaching method in control group, to examine the effect of using CLT activities on year-one students' speaking skills before and after using CLT, and to identify whether or not there is significant difference before and after using CLT on year-one student's speaking ability at Department of English Language, Faculty of Letters, National University of Laos. The study used a pre-experimental design and employed cluster sampling to select a total of 59 students. After the involvement, the control group showed a slight improvement, with only 10% of students reaching the "Good" level. In contrast, the experimental group showed significant improvement 76% of students reached the "Good" level and 24% achieved the "Very Good" level. The average score in the experimental group increased from 53.67 to 80.34, while the control group's score rose slightly from 52.50 to 53.67. The t-test proved a statistically significant difference $(p<0.05)$ between the two groups after the experiment. the t-test results reveal a highly significant difference between the groups' post-test scores $(t=22.192$, $df=43.921$, $p<0.001$, with a substantial mean difference of 26.678 points. The standard error of this difference is relatively small at 1.202, and the 95% confidence interval ranges from 24.255 to 29.101, not containing zero, which further confirms the statistical significance of the findings. These results strongly suggest that the intervention or teaching method applied to the experimental group was remarkably effective compared to the control group's treatment, producing a clear and statistically significant improvement in performance. Therefore, the findings indicated the effect and benefit of the use of the CLT method can help students than traditional teaching methods in improving the students' English-speaking abilities in Department of English Language, Faculty of Letters, National University of Laos.