Future large space telescopes will be equipped with adaptive optics (AO) to overcome wavefront aberrations and achieve high contrast for imaging faint astronomical objects, such as Earth-like exoplanets and debris disks. In contrast to AO that is widely used in ground telescopes, space-based AO systems will use focal plane wavefront sensing to measure the wavefront aberrations. Focal plane wavefront sensing is a class of techniques that reconstructs the light field based on multiple focal plane images distorted by deformable mirror (DM) probing perturbations. We report an efficient focal plane wavefront sensing approach for space-based AO that optimizes the DM probing perturbation and thus also the integration time for each image. Simulation of the AO system equipped with a vortex coronagraph has demonstrated that our approach enables efficient information acquisition and significantly reduces the time needed for achieving high contrast in space.