Ammonia leak is one of the key factors for air pollution, which may cause acute edema, respiratory failure and other diseases harmful to human health. Nowadays, the development of high-performance ammonia sensors has become one of the important means of real-time monitoring and safety warning of ammonia. In this work, three types of molybdenum disulfide with different morphologies of nanoflower, nanosphere and nanosheet were prepared by the hydrothermal method, and three types of MoS₂ ammonia sensors were constructed. The results of gas-sensing experiments showed that among these MoS₂ ammonia sensors with different morphologies, the NH₃ gas sensor made of nanoflowers MoS₂ performed the best performance with a high response value of 7.41% to 10×10^-6 NH₃, while those of the nanosheets MoS₂ and nanospheres MoS₂ sensors under the same NH₃ concentration were 2.01% and 5.11%, respectively. In addition, the nanoflowers MoS₂ sensor also exhibited excellent repeatability, stability and selectivity. The reason for the superior response performance of the nanoflower MoS₂ ammonia sensor is mainly due to the larger surface area, which could provide more active sites for the adsorption of ammonia. This study demonstrates an effective way to prepare high-performance NH₃ sensors with using MoS₂ as the substrate material.