The problem of classification of Aff (2, R )-orbit’s dimensions is considered for autonomous polynomial quadratic differential systems in the case K5≡ 0, where K5 is an invariant polynomial in coefficients and variables. Lie algebra, corresponding to the representation of Aff (2, R )-group in the space of coefficients and variables of the considered systems is constructed [1]. The affine invariant conditions for distinguishing Aff (2, R )- orbit’s dimensions are found. In order to determine these conditions the affine comitans and T-comitants constructed in [2,3,4] were used.