Evolution of the primary phase of spray forming 7055 aluminum alloy during pre-heattreatment before deformation was studied by SEM, TEM and XRD test. The primary phases of as-sprayed 7055 alloy are AlZnMgCu phase and Al7Cu2Fe phase. The AlZnMgCu phases are fine in the grain while the ones on the grain boundary are coarsed. The grain boundary phases formed as a symbiotic microstructure including AlZnMgCu and Al7Cu2Fe phase. When the treat temperature below 400℃, the dissolution of primary phase is less due to the low diffusion coefficient. However, the Zn content has an apparently decline in both intragranular phase and grain boundary phase. When the temperature increases to 450℃，the fine primary phase is completely dissolved, while the coarsened phases on grain boundary transformed to an ellipsoid-like Al2CuMg phase. When treated at 470℃, inner phase has the same dissolved behaviour but the transformation of grain boundary phase to Al2CuMg is avoided. The results show that the evolution of primary phase depends on the second pre-heattreatment temperature.