In this article, indicator of the effectiveness object detection in video surveillance systems (VSS) was proposed. The results of experimental calculations, have been indicated to increase the efficiency of using VSS with video analytics functions. After modeling the obtained expressions in the software package Mathcad and using the main indicators of the conditional software and hardware, it is obvious that the probability of detection of the object (person) by the video surveillance system operator depends on a number of parameters (geometric dimensions of the observed object). , parameters of the video surveillance camera, parameters of the information display device (monitor), features of the visual system of the human operator, the level of his fatigue and level of training, etc.). Areas of further research determine the software implementation of the proposed criterion, analysis of modern models for determining the probabilities of detecting alarming events by video surveillance system operators.Keywords: probability of detection, human operator, criterion, criterion for evaluating efficiency, indicator, indicator of task success.