Radio environment degrades significantly at Nan Shan 26 m Radio Telescope (NSRT) base due to new and upgraded electrical devices on-site and more establishment of surrounding radio communication services. How do we mitigate them effectively? Firstly, a quasi-real time Radio Frequency Interference (RFI) measurement method is employed for RFI detection and spectral analysis based on the layout for potential on-site interference areas and off-site radio communication services. Our investigation at the frequency bands for pulsar observations (1380--1700 MHz) indicates that transient interferences pose the greatest impact on observations. Then we use a portable RFI measurement system for interferences hunting at the NSRT, and the typical characteristics of interferences are analyzed. Secondly, based on the RFI characteristics, main interference sources in the observation room are shielded with shielding cabinets. The results from our shielding efficiency (SE) measurement and evaluation show that these methods work effectively. Furthermore, we propose a Radio Quiet Zone (RQZ) and the regulations for NSRT to mitigate off-site RFIs.