The thermal rate constants for the methyl formate hydrogen abstraction reaction by deuterium was investigated by the multipath canonical variational transition state theory with large curvature tunneling (MP-CVT/LCT). The multistructural torsional anharmonicity factor decreases the thermal rate constants for deuterated reaction R1a and increases considerably for R2a. The path-averaged generalized transmission coefficient is dominated by the characteristics of the lowest-energy paths for both reactions. The MP-CVT/LCT rate constants are in excellent agreement with experimental data (T = 1079-1270 K).