Abstract: The mutant 263-H9 with hypersensitivity to several stress conditions (1.5 mol/L Sorbitol, 0.65 mol/L NaCl and 15℃) was obtained by using transposon mutagenesis in the Saccharomyces cerevisiae strain W303-1A. Unlike other mutants the transposon in 263-H9 was intergenic between GIP2 and YER053C-A. Using gene knockout, a yeast genomic library and other methods, the gene correlated with the salt stress response was identified. The data indicated that the phenotype of 263-H9 was not directly caused by the insertion of the transposon. On the other hand, the hypersensitivity to salt and other stress conditions was due to the deletion of 5 base pairs close to position 936bp in the PBS2 gene essential for HOG signal pathway regulation under salt stress.