Abstract: We  characterized strong Prüfer rings by using semi-regular flat modules. Namely, we proved that a ring R was strong Prüfer if and only if any ideal of R was semi-regular flat module, if and only if any submodule of a semi-regular flat module was semi-regular flat module, if and only if any R-module had an epimorphic semi-regular flat envelope.

Key words: semi-regular flat module, DQ ring, strong Prüfer ring, semi-regular coherent ring