A full modeling of deceleration of α-particles in SiC is carried out using a Monte-Carlo method. The distribution of energy losses in nuclear elastic collisions is calculated. The spectrum has a characteristic asymmetric form and the line width at half peak maximum is 4.62 keV. The final form of a spectral line is obtained by convolution with a Gaussian peak, and including the contribution of ionization fluctuations and noise. The resulting value of the line width was 8.75 keV (at a noise dispersion of detector and equipment of 1.7 keV). The resolution of detectors reached in practice is twice the lowest calculated value. It is shown that charge losses during transport of nonequilibrium carriers through the volume of the detector are insignificant, while a resolution divergence may result from a non-optimized “entrance window”.