Abstract: Methods and techniques allowing to calculate quantitative estimates of level of protection from unauthorized physical intrusion for different informatization objects using various means and protection systems are currently being intensively developed. Generally the quantitative evaluation of protection is represented by a set of probability characteristics, the predominant of which is some integral indicator. Therefore, developing mathematical and simulation models for calculating an estimate of informatization object protection from unauthorized physical access is an urgent task. This model then is used as a part of a complex system of information security. To solve this problem the article presented uses methods of information protection, graph theory and probability theory. The results shown in the article were calculated using Maple system of computer algebra. Scientific novelty of the work is: – in creating a mathematical model for calculation the probability of detecting of unauthorized physical access to information by an alarm system; – in bulding of a simulation model for evaluation of level of protection of informatization object from unauthorized physical access; – in developing of a technique of evaluation of full protection from unauthorized physical access for object of informatization