In order to propose a scientific and reasonable, simple and intuitive， and universal common model for the assessment of ground water quality, an exponential universal formula of power function in logarithm form suitable for multi-indexes was presented by setting up normalized transform for ground water indices. Particle Swarm Optimization (PSO) was used to optimize the parameters in the presented formula. The presented formula was used and compared with some methods in several evaluating cases. The results showed that the formula is free from the restrictions of the kinds and numbers of indices, which has generality and practicality, and provides a new universal and simplified approach to the water quality assessment.
