Small-size milking machines of well known firms differ in the parameters of a vacuum system. Different schemes and techniques are used to connect the vacuum system components into one construction. It affects the variability of the performance figures of the equipment operation. It appears to be difficult to determine the generalized parameters of a vacuum system. Various components of a construction scheme of a vacuum system cause different loss levels of the vacuum pressure. Significant pressure losses in a vacuum system reduce the energetic effectiveness of a milking machine. The researchers have not sufficiently studied the problem of a vacuum system simulation with minimal vacuum pressure losses. A need arises to substantiate the rational construction of a vacuum system of a small-size milking machine. For this purpose, it is necessary to study the schemes of connecting a vacuum pump, a vacuum tank, air lines and a milk bucket into an overall design. The connection of the matched as to the geometric parameters components results in reducing the pressure losses in the vacuum system. The reducing of pressure losses in the vacuum system makes it possible to increase the level of vacuum pressure in the milk bucket. Herewith, the vacuum pump capacity is not changed. The investigation proves that it is expedient to attach the air pipeline under minimum angle to the cylinder of the vacuum tank. It makes it possible to reduce the vacuum pressure losses by 10-45%. It has been established that pressure losses reduce due to the increase in the size of an opening, when the set angle of the air pipeline connected to the vacuum tank decreases. The investigation establishes the increase in pressure losses by 8-11% for the air line with an optimal bending radius. A mathematical model of determining pressure at the inlet of the main air pipeline of the vacuum pump has been received. A rational scheme of the vacuum system of a small-size milking machine has been substantiated.