A parameter combination extreme formula for water safety assessment, which was universal and suited to a number of indicators and several regions, was proposed based on the reference value of all indicators and the appropriate standardization transformation formula. The particle swarm optimization was used in optimization of the parameters in the formula. The optimized combination extreme formula with university was used in case study. The results show the practicality and feasibility of the formula. The combination extreme formula based on standardized indicators was not restricted by the numbers of the evaluation indexes, it provides a new approach to the water safety evaluation model to be universal and simplified.