The estimation of temperature change in a magma chamber during the process of convecting stream interaction was carried out. The streams were presented by the melt or by the mixture of melt with crystals. The equation of temperature change in the chamber provoked by crystallization was obtained which is determined (with accuracy to the coefficient whose estimated value makes up 3.5 102 K) by dependence C(Al2O3) -H (concentration is the function of H - the position in the vertical section of the intrusion) or C(MgO)-H: ΔT(H) ~ const 1 (H) + (3,5 102K)(C(Al2O3))(H) = const2(H)-(3,5 102K)(C(MgO))(H). It was concluded that temperature heterogeneousness may appear in a magma chamber in case of crystallization from the top. The temperature inside the magma chamber may be equalized on the whole volume only in case of intensive convecting intermixing.