The reaction mechanism of linear butadiynyl radical C4H ((CCCCH)-C-1-C-2-C-3-H-4) with methanol (CH3OH) was studied at the CCSD(T)/aug-cc-pVTZ//BB1K/6-311+G(2d, 2p) level. Six different hydrogen abstraction channels were considered, and methyl-H and hydroxyl-H of CH3OH abstractions by C1 atom (M1 and M2) are the two predominant and competitive channels. Further analysis indicated that M1 is a hydrogen atom transfer (HAT) channel while M2 is a proton-coupled electron transfer (PCET) channel. For M1 and M2, the high-pressure rate constants in the temperature range of 100-1400 K were calculated by ICVT/SCT and TST/W methods and the changes of branching ratios with temperature under four pressures (0.1, 1.0,10 and 100 atm) were also considered by Master equation approach. (C) 2014 Elsevier B.V. All rights reserved.