Method: Verification of the additive model was carried out on the experimental data received on prepared in special case(with horizontal dimensions of 70x70 cm and height of 90 cm) an artificial soil monolith with different moisture content layers. All sides of this monolith have been coated by film getting them impervious for evaporation. Each layer of the soil was separated from another by the film to exclude mixing of soil water content on the boundary of layers. The soil material of a monolith has been selected from the top of aggregated horizons of dark-chestnut soil of Saratov Region. For exception of formation inside a monolith of significant air cavities and this soil material was exposed to preliminary processing (a choice of roots and crushing of large blocks), then the soil has been placed in a monolith, thus was made level-by-level (1 cm) compressing for obtaining homogeneous soil body and condensation up to the planned values (gravimetric moisture in a range from 0,08-0,30g/g, density from 1,1 up to 1,38 g/sm3). The plastic tube (1 m height) was installed in the middle of the box to measure the soil water content by TRIME tube probe. Series of scanning measurements of volumetric humidity have been done at various position of a probe on height of a monolith with step on 1 sm. With the purpose of reception of representative given measurements they were carried out several times during three days at four various horizontal positions of a TDR-probe. After the measurements the soil monolith has been disassembled, and from each created layer were selected samples for density and moisture definition by gravimetric method. The model and results: The model simulate measurements of volumetric soil moisture, contained in volume of probe approbation, is based on a hypothesis of additivity of the moisture content, of layers getting in this volume. On this model the program in language VBA was developed. This model provides us a curve of scanning with a set of entrance data and a step of scanning. Experimental values of volumetric and the density of soil layers received as a result of disassembly of a soil monolith, and also size of an active and inactive zone of a probe have been used as the entrance data for the developed program of calculations. Calculations have been carried out for various combinations of size of an active and inactive zone of a probe at a step of scanning 1 sm. As a result of comparison of modeling curves of scanning with experimental, it has been shown, that the best reproduction of first second (factor of pair correlation 0,994) corresponds(meets) to sizes of an active zone laying in a range 15-16 sm.