Abstract: The isomerization and hydroformylation of butene under the catalysis of Rh-BIPHEPHOS were investigated by varying the butene feed and reaction temperature. The results indicate that in the presence of syngas, with 1-butene as feed, more isomerization product (i.e. 2-butene) is detected in comparison with the hydroformylation products, whereas with 2-butene as the feed, the hydroformylation is superior to isomerization. Due to the equilibrium limit between 1-butene and 2-butene, the increase of temperature shows a great positive effect on the isomerization reaction. Furthermore, under the catalysis of Rh-BIPHEPHOS, more n-pentanal is always formed than i-pentanal, as the larger bite angle of BIPHEPHOS restricts the intermediate rearrangement in the formation of i-pentanal.