In this paper, we present an underwater wireless optical communication (UWOC) system with high alignment accuracy based on all-optical acquisition. The system adopts all-optical acquisition technology to achieve underwater acquisition pointing tracking (APT) for rapid establishment of UWOC links and variable divergence angle technology to achieve stable data transmission of UWOC. By this way, the alignment accuracy can be controlled within 1 mrad when the link is established. Thus, the UWOC systems can reduce the laser beam divergence angle to 1mrad for minimizing the intensity loss. So when applied in Jerlov I seawater with 17dBm of transmitting optical power, the underwater equivalent transmission distance can reach more than 150 meters, where the UWOC link can be automatically established and the bit error rate (BER) value can still be zero with a data rate of 1Mbps.