3-Pentanone has been recently identified as a promising biofuel candidate. H-atom abstraction from 3-pentanone by <(H)over dot> and <(C)over dot>H-3 radicals and the subsequent isomerization reactions are important in chemical mechanism of 3-pentanone. In the present study, the potential energy surfaces were calculated at M06-2X/ma-TZVP//M06-2X/6-311+G(2df,2p). The rate constants of these reactions were calculated using the conventional transition state theory (TST) including the multi- structural torsional (MS-T) anharmonicity and tunneling corrections with the Eckart approximation. The results show that the updated rate constants deviate from previous data by up to a few orders of magnitude. Tunneling effect increases the rate constants at low temperatures significantly. Torsional anharmonicity was taken into consideration by the MS-T method. Hydrogen from the methylene in 3-pentanone is easier to be abstracted than from the methyl group. Hydrogen abstraction by <(H)over dot> from the methylene in 3-pentanone is the fastest reaction among them. The calculated rate constants of the five reactions are updated in the Dames-2014 mechanism, and the predictions of ignition delay time of the updated mechanism agree better with the previous experimental data.