From the group statistical theory, a new universal equation is proposed for calculating the surface tension of solution with surface thermodynamics of solution. The simple form of the equation makes it convenient to use and its parameters have obvious physical meanings. With this model, we have explained the experimental phenomena and empirical rules in cited works. Tested for 302 kinds of binary system, the overall absolute average deviation for 3230 data sets is 0.49%, making the model more accurate than those found in the literature. It also accounts for systems unsuitable for reference models because the phase states of the pure components are different under solution condition.