Known methods of a choice of the contractor for implementation of the construction project of the buildingare not fully consider its business reputation. It is caused by lack of mathematical models of the actual level of business reputation of the construction organization for a present situation of time. Relevance of offered approach consists in development of an integrated indicator of level of business reputation in which relative values of factors of reputation, and also their importance for the customer of the project of the building are used. The purpose of work is increasingof efficiency of decision-making at justification of a choice of the contractor on the basis of data on his business reputation. The objectives are achieved by use of the device of expert estimation of levels of factors and their importance in structure of business reputation. It is offered to estimate level of business reputation of the contractor by means of mathematical model of a complex indicator of this property. For receiving possibility of the joint analysis of factors it is offered to use their relative values inrelation to "reference" values. The offered approach took place settlement approbation in relation to processing of results of expert estimation of factors of business reputation of the contractor and showed the working capacity. Two cases – identical and various factors are thus considered. On the basis of these results conclusions are drawn on opportunity and conditions of application of the developed algorithms and model.