This paper presents an approach for design and realization of a smart device for measuring and monitoring ammonia concentration. The developed system included two parts: hardware and software, in which the hardware of the system has been developed based on the ATMEGA328P microcontroller in order to collect data from the ammonia sensor MQ135. Meanwhile, the software is developed for signal processing and warning according to different thresholds. Collected data by the system is then transmitted to a computer via the wireless communication protocol. In addition, an interface is also designed on computers to collect and monitor data from sensors. The developed system allows to measure ammonia concentration up to 300ppm and has been tested not only at the laboratory but also at NPK factory of Lamthao Fertilizers and Chemicals Joint Stock Company. Experimental results show the desired performances of the developed system.