Teat liner in direct contact with the animal's udder has a significant impact on the quality of the milking process and on diseases of the animal's udder. Foreign firms recommend not to carry out maintenance of the teat rubber, but to change it after 2500 milkings due to the high costs of maintaining the working condition of the teat rubber, which inevitably leads to underutilization of the resource. Taking into account the current situation, it is proposed to carry out diagnostic control of the state of the teat rubber on working milking machines in accordance with the developed method and to carry out culling, depending on the technical condition. Determination of the main parameters of the milking machine was carried out using devices to control the stability of the vacuum of the milking machine and to measure the pressure of the teat rubber on the teat. The studies were carried out in laboratory conditions and on a dairy farm. The developed method and technical means made it possible to conduct research and establish the dependence of the pressure on the end of the nipple for domestic teat rubbers. Dependences of the pressure of various types of teat rubbers on the teat on the values of regime parameters have been established. The dynamics of changes in pressure on the nipple during operation was studied. It is shown that the pressure on the nipple during operation can be regulated by both the operating vacuum and the tension of the liner, while the adjustment range is 35% of the range of permissible values. It has been established that teat rubbers can be operated in the mode of optimal pressure on the teat.