The main objective of the paper is to investigate the determinant factors affecting the academic performance of regular undergraduate students of Arba Minch university (AMU) chamo campus students. To meet the objective, the Pearson product moment correlation statistical tool and econometrics data analysis (OLS regression) method were used with the aim of establishing the relationship between factors related to student's background and family background on academic performance of regular undergraduate students at Arba Minch university chamo campus students. The findings proved the existence of significant relationship between gender difference, university entrance exam, studying hours and academic performance (CGPA). The findings also revealed that there was a significant relationship between students former academic back ground,studying hours, and student's behavior on taking of alcoholic drug and chat on academic performance of students. On the basis of the findings, the researcher recommended that emphasis should be taken to improve the academic performance of female students, working at the ground with high school students earlier before they joined in to university and Providing Psychotherapy and supporting alcoholic drug and khat taker students to end the use such drug and Khat will bring more fruit to improve students' academic performance.