As mobile hosts dynamically change their locations, which makes the multicast transmission tree to be rebuilt frequently, the existing reliable multicast algorithms are unsuitable for mobile hosts in wireless IP networks. In this paper, a new basic mobile multicast mechanism called previous network subscription is proposed. Then, a new reliable multicast algorithm supporting mobile hosts is given. Based on hierarchical architecture, this algorithm integrates previous network subscription and remote subscription. An ACK and NAK mixed acknowledgement mechanism is adopted, the lost packets are retransmitted by multicasting, and the NAK suppression is used in the subnet. The analysis and simulation results show that the algorithm has a good performance in terms of retransmission delay, retransmission cost, multicast service disruption, and protocol cost.