Genetic polymorphisms of hemoglobin protein, serum esterase. amylase, ceruloplasmin enzymes were analyzed by the method of starch gel electrophoresis in 116 Che Ju native horses, and phenotvpes and gene frequencies for loci controlling these biochemical traits were determined. The results obtained from the present study were summaritzed as follows; 1. In the hemoglobin(Hb) locus, three different phenotypes AA, Aa and as were founded, presumed to be controlled by two codominant alleles, Hb^A and Hb^a at a single autosomal locus. The distributions of phenotypes were AA type 87.93%, Aa type 11.21% and as type 0.86% It was observed that the frequency of Hb^A allele(0.935) was remarkably higher than that of HP allele(0.065). 2. Considering esterase(Es) isozyme locus, four phenotypes FF or F0, II or IO, FI and OO were demonstrated, and these isozyme could be explained by the action of three autosomal alleles, two codominant alleles, Es^F and Es^I and one recessive allele, Es^O lacking a detectable gene product. The phenotype distribution was 23.28% for FF or FO, 34.48% for II or IO. 38.79% for FI and null phenotype OO was lower than 5%. At the gene frequencies for locus controlling Es molecular form, the Es^I with a frequency of 0.470was the most common allele. Secondly. the Es^F allele frequency was 0.374 and the silent Es^O allele frequency was 0.156 and the Fs^S allele was not recognized. 3. The amylase(Am) and ceruloplasmin(Cp ) loci were observed to lack any individual variation. Therfore, these loci were defined to be monomorphic.