Abstract A simple and recyclable biphasic rhodium catalytic system for the hydroformylation of long-chain alkenes is performed with the presence of Rh/TPPTS (trisodium tris(m-sulfophenyl)phosphine) in highly polar formamide for the first time. This work investigated the phase behavior of 1-octene, 1-nonanal and formamide, as well as the factors affecting the catalytic performance and catalyst recovery. Two phases were fully separated with distinct interface, allowing facile recycle of catalyst-containing formamide solution by decantation. Hydroformylation could be carried out under mild condition with turnover frequency and aldehyde selectivity up to 950 h−1 and 97 %, respectively. The catalyst could be reused for at least 40 runs without obvious activity and selectivity decline. No extra rhodium or TPPTS was needed during the cycle runs, and the average rhodium loss for each cycle was as low as 0.02 wt%. This system has also been successfully applied to the hydroformylation of crude higher α-olefins with high conversion and rhodium reservation, which were just distilled from Fischer-Tropsch synthesis with 64.7∼81.0 % fraction.