Abstract: The photocyclization quantum yield of traditional diarylethene systems is always limited to 50% (mole fraction) due to the inseparability of the parallel (p-) and anti-parallel (ap-) conformers. However, it is possible to block the conversion between the two conformers by increasing steric hindrance between the side aryl groups and ethene bridge, thus enhancing the photocyclization quantum yields. Herein, based on the sterically-hindered bisbenzo(thiadizole) ethene bridge, we fully compared the steric effect of side thiophene rings, and got insight into the electronic effects of substitution groups, like the electron-donating, such as anisole unit and the electron-withdrawing pyridine units. The parallel and antiparallel conformers of compounds 1 and 3 can be separated successfully upon introducing the sterically hindered methyl group to the β-position of thiophene rings, thus greatly improving their photocyclization quantum yields, higher than 50% (mole fraction). Moreover, the incorporated steric hindrance of β-methyl groups on thiophene rings results in lower thermal stability of 1c and 3c. In contrast, 2c and 4c show good thermal stability which can be attributed to the relatively small steric hindrance and intramolecular hydrogen bond. When compared with the electronic effects, the electron-withdrawing effects of pyridine units brings forth the higher thermal bleaching rate of 1c than that of 3c containing the electron-donating anisole units.