Abstract: According to the batch experiments on cadmium releasing behaviors in paddy soil under different acid rain conditions, the releasing process of cadmium absorbed in the soil can be divided into two steps, i.e., the fast reaction and the slow one. Several frequently used dynamics equations and anti-trigonometric function equation established in this paper were adopted to fit the data obtained from the leaching test, respectively. Compared with the frequently used equations, the anti-trigonometric function equation can describe very well the Cd releasing process in paddy soil under the impact of different acid rain conditions, and the polynomial equation is also suitable for describing this process.