Agricultural production in Ethiopia is predominantly rainfed. And variation of rainfall in space and time affects the agricultural production system. Due to this it needs accurate measurement and study on the rainfall variation. So, this paper main aim is to investigating the rainfall variation as well as its effect on the selected main crops production on the Banja wereda. The major crops which are used in the investigation of the relationship between the rainfall variability and the relationship with different time steep and different space were considered with crops production. The rainfall data are taken from the four inter stations and one from the neighboring wereda stations to represent the whole study area. And the cop’s data is taken the whole wereda crops production. The rainfall data collected stations are Injibara, Kessa, Askuna and Kidamaja from the study area and Gundil from neighboring wereda stations for the time period of 21 (1996-2017) years. Then the data was subjected to correlation analysis with production as the dependent variable and rainfall data as independent variables. The rainfall data that have correlated with crop production were subjected to test for the significance of the correlation analysis in order to understand the effect of the rainfall on the crop production in that study area. Finally, in the study, total annual, Kiremt and Belg Arial rainfall are retreated with main crops production of potato, Teff, Wheat and Barely over the period of 6 years (20122017). The result shows low significant correlation between total annual, Kiremt and Belg rainfall, and production of those cereals. This analysis, however, includes small number of sample data and thus doesn’t include data are occurred in the wereda. In addition, in the analysis some factors are considered. But other agronomic factors are ignored. Therefore, large number of sample data and consideration of other factors should be used in future studies.