Higher alcohols synthesis (HAS) directly from syngas, as environment-friendly liquid fuel or fuel additives, is regarded as a “green” route. It is essential for catalyst design to study reaction mechanism of HAS. To obtain carbon chain growth mechanism, the reaction network of HAS from syngas on CoCu(100) surface was systematically studied by density functional theory (DFT) calculation and kinetic Monte Carlo (kMC) simulation. Firstly, the energetics of the key elementary reactions of HAS on CoCu(100) were obtained by DFT calculation. And then the reaction processes of carbon chain growth were simulated with kMC method. Finally, the reaction mechanism of carbon chain growth on CoCu(100) was analyzed. The results show that CH is not easy to generate and easy to transform into CH2 on CoCu(100). CH2 and CH3 are easy to form and they are the key intermediates to achieve carbon chain growth. The addition of Co can promote the CO bond of CH2O scission to form CH2, inhibit the formation of CH3O, change the reaction pathway on CoCu(100), and thus improve the selectivity of C2+ alcohols.