This study was carried out to determine of the relationships between California Mastitis Test (CMT) with milk yield and milk composition and also aimed to determine of effects of the various in the assessment of test scores on the diagnosing of subclinical mastitis, milk yield and compositions in Jersey cows. Totally 51 Jersey cows were examined to determine of the subclinical mastitis by CMT and milk samples collecting from each of the four udder lobes of each animal were taken and scored as negative (-), suspect (+1), +2, +3 and +4. In addition, it was determined for fat, protein, lactose, dry matter, non-fat dry matter and freezing point of milk in the sample. Two different groupings were performed for assessment of the CMT data. To first groupings, three different sub-groups creating were performed named as negative (group 1), suspect (group 2) and other scores (group 3). Second grouping in evaluate for suspect scores were performed for regarding as accepting scores CMT positive (CMT-I) and negative (CMT-II). In CMT-I group those with - (negative) values for all lobes were termed CMT negative, those with +1 (suspect) to +4 in any lobe were termed CMT positive; in CMT-II group those with - (negative) or +1 (suspect) in all mammary lobes were termed CMT negative and those within +2 to +4 in any lobe were termed CMT positive. The differences among lactose and freezing point values of the milk in three CMT score groups were significant (P<0.05). In addition, the relationships between CMT scores and fat, freezing point (P<0.05), lactose (P<0.01) were significant. The differences of the groups for CMT-I and CMT-II were found to be significance within the groups (P<0.01) and with the groups (P<0.05). Besides, the differences between milk fat and dry matter values of the CMT positive and CMT negative cows in CMT-I groups were significant (P<0.05). It can be conclude that CMT score was related between lactose and fat, with the freezing point of milk. Therefore, it can be specified that decreasing of lactose and freezing point of milk also increasing of fat may be approve of the indicator of mastitis. Furthermore, observing of the hight ratio for healthy cows was caused by CMT scores of the differences of various assesments and it was also causing to prevent from the determination of changing components including of the milk fat, total dry matter. Because of the these reasons, it is take necessary step to standardization of the assesment of CMT scores to avoid underestimate for the quality of milk and milk product due to the fact that preventing from arising of risk in the human health.