The present study was carried out to investigate the blood markers of Cheju horses. The blood protein types (biochemical polymorphism) were tested from 73 Cheju native horses (CNH) and 118 Cheju racehorses(CRH) by horizontal polyacrylamide gel electrophoresis (HPAGE), isoelectric focusing (IEF) and starch gel electrophoresis (SGE). At the same time, their phenotypes and gene frequencies were studied. The biochemical polymorphism phenotypes observed with high frequency were A1B-KK(97.3%), ALB-AB(49.3%), AP-SS(100%), ES-II(30.1%), GC-FF(87.7%), HB-BIBI(49.3%), TF-F2R(41.1%), TF-EF2(8.2%), PGD-FF(97.3%), PGM-SS(50.7%), GPI-II(74.0%) in CNH, While A1B-KK(99.2%), ALB-BB(50.8%), AP-SS(99.2%), ES-II(42.4%), ES-IS(14.4%), GC-FF(95.8%), HBB-IB II(39.8%), TF-F2R(21.2%), PGD-FF(77.1%), PGD-SS(4.3%), PGM-SS(72.9%), GPI-II(90.7%) in CRH. Alleles observed with high frequency were $AlB^{K}$(0.986), $ALB^{B}$(0.616), $AP^{S}$(1.000), $ES^{I}$(0.479), $ES^{F}$(0.274), $GC^{F}$(0.938), $GPI^{I}$(0.856), $HB^{BI}$(0.685), $PGD^{F}$(0.993), $PGM^{S}$(0.753), $TF^{F2}$(0.404), $TF^{R}$(0.397) in CNH and $AlB^{K}$(0.996), $ALB^{B}$(0.720), $AP^{S}$(0.996), $ES^{I}$(0.661), $ES^{F}$(0.203), $GC^{F}$(0.979), $GPI^{I}$(0.936), $HB^{BI}$(0.534), $PGD^{F}$(0.864), $PGM^{S}$(0.852), $TF^{F2}$(0.428), $TF^{R}$(0.272) in CRH. $TF^{E}$(0.041) allele and silent gene($ES^{I{^*}}$ : 0.014) were observed in CNH. The mean heterozygosity in CNH and CRH was observed 0.2974 and 0.2864, respectively.