The invention relates to a modeling method and system of valve groups in a two-phase fluid network model. The modeling method comprises the steps that the fluid density and the current valve position of each valve of each valve group are obtained; the current flow capacity of each valve is calculated according to the fluid density and the current valve position of each valve of each valve group; the comprehensive flow capacity of each valve group is calculated according to the current flow capacity of each valve of each valve group; a branch grid of each valve group is established in a simulation system according to the comprehensive flow capacity, wherein the branch grid comprises two nodes and a branch connected between the two nodes and equivalent to the valve group. Due to the fact that each valve group is divided into one branch grid and the two nodes and the comprehensive flow capacity of the branch is obtained by adopting an algebraic method according to the fluid density and the current valve position of each valve of each valve group, the number of the nodes is decreased, and the calculation amount can be decreased. In addition, the number of the nodes is decreased, data points needed to be monitored on site are also decreased, and accordingly the cost is reduced.