The objective of the paper was to analyse (under pressure oscillations) vacuum fluctuations within the cycle in the milking apparatus equipped with (collectors) claws with a variable volume of the milk chamber at the alternative milking to the upper (milk pipeline) milkline and to the (bulb) bucket in the conditions of simulated mechanical milking and to develop a mathematical formula for their determination. Measurements were carried out in the laboratory conditions at variable mass intensities of liquid flow (within 0-8 kg·min -1”), for four volumes of (collectors) claws (500, 300, 150 and 45 cm 3”) and three values of system (under pressures) vacumms (44, 46 and 48 kPa). With the use of statistical analysis a significant (impact) effect of independent variables of experience (except for (under pressure) ) on the (under pressure oscillations) vacuum fluctuations within the dp cycle was proved. The lowest values of (under pressure oscillations) vacuum fluctuations within the cycle were reported at the use of the (collector) claw with 500cm 3” volume. Using the multiple regression method with step elimination of independent variables based on the research results a mathematical and statistical model was constructed for determination of the (under pressure oscillation) vacuum fluctuation within the cycle, which takes a character of 3-parameters empirical equation in the form of dp = 4.11 + 0.93Qm + 1.02H – 0.01Vk with coefficient of determination R 2” = 0.77.