Introduction: Intraocular lens (IOL) implants are monofocal and trifocal lenses which helps to clear up the vision after cataract surgery. Goal: In this work, we aimed to compare the monofocal and trifocal IOL implantation during phacoemulsification surgery. Materials and Methods: This study was conducted on 133 participants. Females comprised n=81, mean n=52 into equal groups. Preoperative and Postoperative cataract surgery UCVA and BCVA were measured and compared during the after 1 day, week 1, 2 weeks and month1. Statistical analysis: The results of the study were processed using the SPSS 25.0 program after coding the data and checking for typographical errors. The normality of the data distribution was tested by inspecting a histogram. Categorical variables were compared using the chi-square test or Fisher's test. Statistical significance was determined at a p-value lower than 0.05 Ethical statement: The study was approved by the Research Ethics Committee of the Mongolian National University of Medical Sciences (No.2021/05/21). All patients provided written informed consent before participating in this study. Results: The mean preoperative UCVA was 1.09±0.45D in monofocal IOL group, 0.99±0.49D in trifocal IOL group. At the first week: The mean postoperative UCVA at one week was 0.34±0.29D and 0.27±0.17D, in each group respectively. The mean postoperative BCVA in the first week was 0.28±0.27D and 0.20±0.15D in each group respectively. The mean postoperative UCVA at 1 month was 0.27±0.24D and 0.15±0.16D in each group, while BCVA was 0.26±24.94D and 0.06±0.63D.There was a highly significant statistical difference between the result of UCVA preoperative and the results of UCVA at the early and last postoperative follow up. Conclusion From our results, the best corrected visual acuity and was better for Trifocal group than Monofocal group. It is evident that post-operative near UCVA and BCVA was statistically significant at monofocal and trifocal groups.