In this paper, Cp*Ir (III) Complex and acid co-catalyst system was developed. By using Cp*Ir and γ-Al2O3 (Lewis acid), 5-hydroxymethylfurfural (5-HMF) can be converted efficiently to 3-hydroxymethyl cyclopentanone (HCPN). Meanwhile, Cp*Ir and Brønsted acid can promote conversion of 5-HMF to 1-Hydroxy-2,5-hexanedione (HHD). The effect of Lewis acid and Brønsted acid on the hydrogenation of furan derivatives was studied. Mechanism of conversion of 5-HMF to HCPN was discussed in detail and mechanism proposed by our predecessors was revised. Instead of being an intermediate for the formation of HCPN, it is believed that, HHD is a product of another reaction pathway. HHD condensed via Aldol reaction to produce 3-methylcyclopenten-2-ol-1-one (MCP) instead of HCPN. Under the promotion of Lewis acid, 5-HMF firstly convert to the precursor of HHD. After that, the reaction is through 4 π-electrocyclic ring closure process and HCPN was formed ultimately. Furthermore, we found that our Cp*Ir and acid co-catalyst system is suitable for a variety of furfural compounds. By using Cp*Ir, Brønsted acid can promote conversion of furfural compounds to straight chain ketones and Lewis acid can promote the rearrangement of furfural compounds to cyclopentanone derivatives.