This study was carried out to evaluate the effects of different plots sizes on the estimation of wheat yield in New-Halfa scheme. We applied crop cutting method to estimate wheat yield and multi-stage stratified sampling method for the sampling. We use a farm survey data with different plot sizes, in the four villages within the Scheme, and for season 2009/2010. The analysis of variance (ANOVA), multiple comparison, standard deviations, standard errors, and coefficients of variation were used in analyze the results. Results showed no significant differences between large and medium size plots in yield estimation. However, there were significant differences between large and small plot sizes and between medium and small plot sizes with respect yield estimation. Higher crop yields were obtained in small compared to large and medium size plots in both strata. As plot size increases, the estimated yield and standard deviation of yield decreases in the two strata. The yield estimation attains a stable value when the plot size is significantly large and it is not recommended to estimate wheat yield with plot sizes less than 42 square meters.