Based on a general architecture of erasure error correction under strict delay constraints for realtime wireless multicast, we contribute a simple method for analyzing quantitatively the effect of packet size on the throughput performance of Hybrid error correction (HEC) schemes. We then propose an adaptive HEC scheme for maximizing its throughput with Variable packet size (VPS). By analysis, it is found that the throughput performance of the adaptive HEC scheme with VPS is influenced deeply not only by the variation of packet size, but also by the change of the weight of overhead messages in packets. It indicates that the packet size and the weight of overhead messages should be designed jointly for achieving the optimum throughput performance. Finally, comparing with those schemes with fixed packet size, the analysis results show that the adaptive HEC scheme with VPS can improve the throughput by about 20% in some cases.