In this article, the optimization parameters of maintenance strategy "on condition" with a constant frequency of control is carried out. During the operation of complex technical objects, as a rule, maintenance is carried out to maintain the required level of object reliability. It is known that the most effective principle of maintenance organization is “maintenance by condition” (MC), according to which maintenance operations are carried out only if it is required by the actual technical condition (TC) of the object. In order to be able to determine the actual TC of an object during operation, it is necessary to develop and “embed” in the object tools for measuring the determining parameters of the most unreliable elements even at the stage of its creation. To do this, the developer needs mathematical models with which to estimate the expected costs of embedding measuring instruments and the expected gain from maintenance during the operation of facility. Currently, there are no satisfactory models that allow one to obtain such estimates. In this article, an attempt is made to partially fill this gap - models are proposed that allow predicting the indicators of reliability and cost of operating an object, taking into account MC. The article also developed methods to determine the optimal parameters of various maintenance strategies. The problem is that when developing such facilities, all issues related to maintainability and maintenance should be addressed already at the early stages of the design of the facility. If you do not provide in advance the necessary hardware and software for integrated monitoring of the technical condition (TC) of the object, do not develop and “embed” maintenance technology into the object, then it will not be possible to realize in the future a possible gain in the reliability of object due to maintenance. Since all these issues must be resolved at the stage of creating an object (when the object does not yet exist), mathematical models of the maintenance process are needed, with the help of which it would be possible to calculate the possible gain in the level of reliability object due to maintenance, to estimate the cost costs required for this. Then, based on such calculations, make a decision on the need for maintenance this type of objects and, if such a decision is made, develop the structure of maintenance system, choose the most appropriate maintenance strategy, and determine its optimal parameters.