With the rapid development of 5G networks and the significant in-crease in the number of users, this paper explores the feasibility of applying these low-frequency resources to 5G systems, considering the significant advantages of low-frequency band (e.g., 900 MHz) spectrum resources. Our goal is to optimize cost-effectiveness in 5G network construction by reducing signal propagation loss, expanding coverage, and reducing network deployment costs. How-ever, to use the 900 MHz band efficiently and safely, the adjacenting frequency interference problem must be taken into account. In this paper, we focus on the impact of reconfiguring the 900 MHz band in 5G NR systems on the adjacenting frequency interference in IoT systems to ensure the reasonable and safe use of spectrum resources and avoid potential co-channel and adjacenting frequency interference problems, so as to maintain the orderly use of radio waves.