Genetic parameters for milk,fat yield and age at first calving of Chinese Holsteins in Heilongjiang were evaluated using multiple-trait restricted maximum likelihood procedures with an animal model. Data consisted of records of 2496 Chinese Holsteins first lactation cows collected from 1989 to 2000. The model included 21herd effects, four calving season effects, nine age at first calving effects, 6697 animal effects. (Co)variance components of milk yield ,fat yield and age at first calving were estimated with the software package for variance component estimation(VCE) by an animal model. The heritabilities were 0. 14.0. 21,0. 38 for milk yield ,fat yield and age at first calving ,respectively. ihe estimates of genetic correlation between milk yield and fat yield,age at first calving were 0. 96,-0.29.respectively. The estimate of genetic correlation between fat yield and age at first calving was-0.28.