Multicast is a popular way of data dissemination. How to monitor the multicast traffic is essential to tackle network bottlenecks and performance woes. The original In-band Network Telemetry (INT) provides a low-latency and fine-grained monitoring solution. However, to apply INT directly to multicast traffic causes problems like telemetry data redundancy and network bandwidth waste since the telemetry data collected from the same device may be duplicated several times. In this work, we propose MPINT, a telemetry framework dedicated to multicast traffic monitoring, which is cost-effective with minor bandwidth overhead. Evaluation shows, compared with the original INT, MPINT reduces the INT bandwidth overhead by 80% and eliminates 50% of the telemetry data uploaded to the controller. In addition, it takes less than 0.5s to complete the entire multicast tree recovery and packet loss estimation on 180 devices.