A new type of pneumatic grid is designed， actuator which can realize bidirectional bending with fixed angle. Firstly， a nonlinear mechanical model of the bidirectional bending soft actuator is established， and three piecewise functions are obtained， each of which represents functional relationships between the bending angle and the driving pressure of the soft actuator at corresponding stages. Secondly， the relationship between the bending angle and driving air pressure of the soft actuator is described by a simulation method. By comparing the pressure and bending angle of the two soft actuators， it is found that the difference lies in the elastic potential energy squeezed between the airbags on the uninflated side. Finally， the soft actuator model with two bending directions is made experimentally and the theoretical model is verified by experiments. The results show that the nonlinear modeling and design of the bidirectional bending pneumatic grid soft actuator proposed in this study are feasible.