Aiming to boost the throughput performance in mobile networks, network-coded multiple access (NCMA) has been proposed as a new framework in non-orthogonal multiple access (NOMA). Normally, user-centric design is adopted in NCMA to allocate the same power to different users. However, devices and the corresponding messages may have different quality-of-service (QoS) requirements (such as delay or throughput) due to the potential content diversity in Internet of Things (IoT) networks. In this paper, we present a power-diverse NCMA (PD-NCMA) system. In particular, a two-stage framework in NCMA downlink is adopted. Based on the throughput requirement of content, messages are given different levels, and content-centric clustering is solved dynamically in the first stage. Then, power allocation in each cluster is realized in the second stage. Numerical results demonstrate the feasibility of the proposed PD-NCMA, and the throughput of PD-NCMA significantly outperforms the traditional NCMA system.