Two highly soluble aromatic polyimides were synthesized successfully from a diamine with two ,tert,-butyl groups (MBTBA) and dianhydrides with a thioether or sulfone moiety (DTDA and DSDA). Both of them showed excellent solubility in common solvents such as chloroform, tetrahydrofuran and dioxane at the room temperature. The number-average molecular weight was 6.0 × 10,4, and 8.3 × 10,4, according to gel permeation chromatography relative to a polystyrene standard, and the polydispersity index was 1.80 and 1.82 respectively. The glass-transition temperatures of them were 286℃ and 314℃ (or 315℃ and 358℃) respectively, as measured by differential scanning calorimetry (or dynamic mechanical analysis). The 5% weight loss temperature of both was near 490℃ in N,2, by thermogravimetric analysis. These results indicated that the ,tert,-butyl pendent groups reduced the interactions among polymer chains and the thioether or sulfone moiety was flexible which may improve their solubility in conventional organic solvents without the loss of thermal stability. Transparent and flexible films of the two polyimides were obtained ,via, solution casting. The MBTBA-DTDA membrane had higher storage moduli than those of the MBTBA-DSDA membrane.