Abstract: The transient characteristics of the solution reactor were analyzed by use of the point reactor theory and the 3D neutron transport theory respectively. The bubble model and temperature model were based on the experiment. Simulations were performed under different work conditions and with different reactivity introduced. The steady power level of solution reactor and the power fluctuation under accident conditions were obtained. Numerical results show that the model based on the point reactor kinetic equations and reactivity feedback mechanisms has a high calculation speed and can be used to perform online simulation of solution reactor, the model based on the 3D neutron transport theory has a high calculation accuracy and acceptable calculation speed and can be used to perform detailed safety analysis.