Background: Diarrhea is defined as the passage of loose or watery stools at least three times in 24 hours or more frequently than normal. Diarrhea is one of the leading causes of child hood morbidity and mortality in developing countries about 5million death occurred each year 80%of which occur in children less than two year. In Ethiopia diarrhea is the leading cause of under two year child morbidity and mortality. Ethiopia still has gap to fill this gap for advocacy for strategic to improve health status among under two year children .this result has great significance in the national and regional level for advocacy and program evaluation . Objective: to assess magnitude of diarrhea and associated factor among under two year children in Ethiopia Methods; study based on Ethiopia demographic health survey 2016data .from this data under two year children were used as study population .selected data file used to answer study objective. Data were weight before analysis form complex sample plan file form for analysis .each variable selected from the data set and recoded when it is necessary. Description the population used unit-variable analysis. Bi-variable analysis by using binary logistic regression for identifying a variable candidate to multivariable logistic regression analysis bi-variable analysis those significant value less than 0.20 interred to multi-variable analysis. To identify associated factors on the dichotomous dependent variable by estimating the odds ratio. Software STATA version, 14 and SPSS V25 used for analysis Result; Total of 4042 children were included among age group 0-24month. From this only 833(12.1%) live in urban the rest live in rural. Diarrheal disease Prevalence [612(16.2%) 95%CI(14.3-16.3)] .Across the region highest incidence diarrhea in Amhara region [77(21.39%) ,95% CI,[16.65-27.04)] the lowest, Addis Ababa [18(9.12%95%CI,[5.5-14.57] the prevalence higher in age group 6-11 month[186( 22.5%), 95% CI [18.35-27.31].Factor associated to diarrheal. Oromia,(AOR=0.62,95%CI[0.41-0.93]),Bishangul (AOR=0.61,95%CI 95%,0.38- 0.81]) Somalia (AOR=0.5295%[0.33-0.81],Harari(AOD=0.42,95%ci[0.23-0.75],AddisAbaba (AOR=0.4,95%CI[0.21-0.75]) as compared to Tigray region . Diarrheal disease had significant association among age group .The odds diarrheal disease among agerange6-11month (AOR=2.43, 95%ci [1.76-3.35], age group, 12-18month (AOR=2.63, 95%CI [1.72-3.24], 19- 24month, (AOR= [1.42-2.94]). being wasted (AOR=1.3 95%CI[1.01-1.66] as compared to not wasted. CONCLUSION AND RECOMMADATION; preventing from wasting children’s can prevent diarrheal attack. Mother shall prevent their child from wasting .study finding has significant implication for public health practice both in programmer design and evaluation and for further research. KEY words diarrhea disease, associated factor, under two children, Ethiopia