Genetic variation of six microsatellite loci BM4505, BM1905, BM1443, BM415, BM143 and BM711 which were closely correlated with milk composition traits was analyzed in 200 Beijing Holstein cows by nondenaturing polyacrylamide gel electrophoresis. Allele frequency, heterozygosity, polymorphic information content, effective number of alleles of the six microsatellite loci were calculated. Relationships between six microsatellite loci and milk composition traits in Beijing Holstein cows were preliminarily analyzed by least squares linear model. The results indicated that microsatellite BM4505 significantly correlated with fat percentage and dry matter percentage; microsatellite BM1905 significantly correlated with protein percentage and lactose percentage; microsatellite BM1443 significantly correlated with protein percentage; microsatellite BM415 significantly correlated with fat percentage, protein percentage, lactose percentage and dry matter percentage; microsatellite BM143 significantly correlated with protein percentage and lactose percentage; microsatellite BM711 significantly correlated with fat percentage. 225 bp/225 bp at BM4505, 168 bp/168 bp at BM415 and 190 bp/190 bp at BM711 were the most favourable genotypes for fat percentage. 201 bp/201 bp at BM1905, 163 bp/163 bp at BM1443, 168 bp/168 bp at BM415 and 110 bp/110 bp at BM143 were the most favourable genotypes for protein percentage. 201 bp/201 bp at BM1905, 168 bp/168 bp at BM415 and 108 bp/108 bp at BM143 were the most favourable genotypes for lactose percentage. 225 bp/225 bp at BM4505 and 168 bp/168 bp at BM415 were the most favourable genotypes for dry matter percentage.