Abstract: Test day milk yield records of 68956 first-parity Holstein cows were used to estimate genetic parameters for milk yield. Comparison of breeding value of two evaluation method include test day and classical model (305 days) indicated that the EBVs for TD milk yields are closely correlated with EBVs for 305 days milk yields. Genetic correlations between individual test days and 305 days were high. Results suggested that test day milk yields, mainly in mid-lactation, can be used of 305 days milk yield in genetic evaluation. the heritability estimate of milk yield under the TD model is lower than the corresponding estimate for 305-days milk yield.