The beaconless inter-satellite laser communication system (BILCS) does not to configure beacon light components, and directly applies signal light with small divergence angle to pointing, acquisition and tracking (PAT), which is beneficial to reduce the weight, volume, power consumption and manufacturing cost of the terminal, and meet the development requirements of commercial spaceflight and LEO satellite space laser network. To overcome the existing shortcomings of long scanning time and difficult acquisition of BILCS, satellite attitude change, measurement accuracy and terminal positioning error were taken into consideration, the scanning field of uncertainty was numerically computed, the beaconless scanning-acquisition process was designed, the coupling relationship of the control bandwidth of the coarse and refined scanning mechanism, scanning step size, planning path and the light coverage area was quantitatively analyzed, a simple and reliable coarse-refined combined spiral scanning method based on beaconless was proposed. Simulation results of typical environment demonstrate that the average acquisition time is less than 20 s, and the acquisition probability is more than 95% by this method, which effectively improves the BILCS scanning efficiency, and can satisfy the requirements of the future LEO satellite space laser network to rapidly establish laser communication link.