Abstract: Accelerated flow past an NACA 0015 airfoil at an angle of attack of 30º during accelerating period was studied numeri- cally. The finite volume method was used to simulate the two-dimensional unsteady incompressible viscous flow. Two uniform ac-celerations of 50 mm/s² and 100 mm/s² were used to investigate the transient flow; the final uniform velocity was 100 mm/s for both cases and the Reynolds number was about 8000. The structure and development of transient flow were presented, and the effect of acceleration on flow structure was evaluated. The results of computations show that the structure of unsteady flow is complex during both the acceleration phase and the constant velocity phase. The separated flow structure during accelerating period differs from that of the steady state. The separated flow and the vortex structure and intensity are dependent upon the acceleration magnitude.