The disclosure provides a medical big data analysis method and apparatus. The method comprises: a sign symptom expressed by a vector h is received; sub space in which a patient is located in medical big data is located by using the sign symptom as a feature, wherein a matrix D is used for expressing a case set in the big data, D is equal to [D1, D2, ...,DM], the Di expresses ith sub space and thei is larger than or equal to 1 and is less than or equal to M, and the location includes calculation of a formula: h=DX; and semantic consistency of the sub space is analyzed to analyze the probability P1 of location of the patient in the specified sub space. In addition, on the basis of an evidence transfer score on a medical mapping knowledge domain, the probability P2 of location of the patientat a specified node is analyzed. The probability P of location of the patient in specified sub space or at a specified node is determined according to a formula: P=alpha+P1+(1-alpha)*P2, wherein thealpha expresses a harmonic parameter and is larger than 0 and is less than 1. Therefore, the accuracy of the analysis can be improved; and the condition of the patient can be analyzed based on the symptom at first time and thus the patient can be checked in an oriented manner, so that the cost is lowered and the efficiency is improved.