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In order to study the hydrofoil cavitation characteristics in the process of accelerated flow, detached eddy simulation (DES) and homogeneous cavitation model were employed to simulate the unsteady flow around NACA66 model at attack angle of 5.8°. The cavitation number was 0.99 and the corresponding Reynolds number was 8×105. The characteristics of cavitation evolution and flow field structure were obtained in the case of two different accelerations (a1=5m/s2， a2=2.5m/s2). Different numerical simulation results were obtained by studying different accelerations. Cavitation was first born in the leading edge of the hydrofoil, and grew after a period of time and finally separated. Then the cavitation in the leading edge was reduced and the cavitation at the tail of the hydrofoil was increased and backward spread until rupture. Cavitation was first generated at around 0.6 times of total acceleration time and finished a cycle at about 1.12 times of total acceleration time. Oscillation ranges of the lift coefficient became large and the range of the drag coefficient was small with the increase of acceleration. Using small acceleration, the cavitation developed more slowly. The simulation results obtained by DES turbulence model were more close to the experimental values than those obtained by homogeneous cavitation model. The research results can provide reference basis for cavitation characteristics study of hydraulic mechanical startup process.