A multicast key distribution method, an update method, and a base station based on unicast conversation key, the distribution method includes the following steps: 1) the base station composes groups of multicast key distribution; 2) the base station broadcasts the groups of multicast key distribution to all terminals; 3) the terminals acquire the multicast conversation key by calculating. The present invention solves the problem that the efficiency of the multicast key distribution based on unicast conversation key is low in the prior art, and provides a multicast key distribution method based on unicast conversation key.