Using the extended Poincar-Lighthill-Kuo perturbation method, we study the interaction between two ion-acoustic solitary waves with different propagation directions in a two-dimensional hot ion plasma, and obtain two KdV equations for solitary waves in both ξ and η directions. We also obtain the phase shifts and trajectories after the collision of two solitary waves with an arbitrary angle. The effects of the ratio of ion temperatures σ, the ratio of heat capacities γ and the angle α on the phase shifts are studied. The results suggest that these parameters can significantly influence the phase shift of the solitary waves. Moreover, there are compressive solitary waves in such a system.