To study the arcless electrical ignition mechanism of hydroxylammonium nitrate (HAN)-based liquid monopropellant LP1846 droplet, based on the two step irreversible chemical reaction mechanism, at the same time, considering the changes of physical parameters with temperature, the numerical simulation for the arcless electrical ignition process of single HAN-based liquid monopropellant LP1846 droplet was performed in the atmospheric environment combined with the related experiments. Results indicate that, according to the variation of reaction rate and temperature distribution, when maximum load voltage is 80 V, the arcless electrical ignition process can be divided into three feature stages: preheating (0~695 ms), thermal decomposition (695~805 ms) and combustion (805~1000 ms). At the preheating stage, the droplet is spherical and the center temperature rises slowly. At the thermal decomposition stage, the reaction occurs in the center of the droplet and develops outwards, the droplet expands and the umbrella distribution of temperature gradient appears inside the droplet. At the combustion stage, the flame is spawned inside the droplet. LP1846 burns vigorously, forming a large amount of products. The temperature of the flow field first increases and then decreases. Ignition delay time decreases with the increase of maximum load voltage. The simulated results has the same trendline of change with the experiment data, and the maximum error is 2.9%.