Achieving the real-time, low-cost, portable and accurate NH3 detection is of great importance in industry owing to the toxicity of NH3. In this paper, Pt NPs@MIL-101-NH2 composites modified screen-printed electrodes (SPEs) were prepared by solvothermal method and ionic liquids [BMIM][BF4] were used as electrolytes. Finally, the prepared Pt NPs@MIL-101-NH2/SPEs were combined with a miniature electrochemical workstation to construct a novel electrochemical NH3 sensor. The experimental results showed that Pt NPs@MIL-101-NH2 has excellent adsorption capacity for NH3, and the sensor has good linearity in the range of 0.7–600 ppm with low limit of detection (0.58 ppm) and fast response time for 10 ppm NH3 (8.0 s). Furthermore, this sensor also possesses excellent stability, reproducibility, anti-interference and accuracy. The synthesized Pt NPs@MIL-101-NH2 nanocomposite was proved to be an excellent candidate for constructing high-performance NH3 sensor for industry.