•The spin friction between magnetic films was originally studied by a DFT method.•The friction obviously decreases after introducing spins.•The spin exchange interaction determines the size of spin friction.Employing first-principles approach within density functional theory (DFT), spin friction properties of Co monolayer sliding on Mn/W(110) substrate were investigated (Wolter et al., 2012) [22]. The magnitude of spin friction is obtained by calculating the friction difference between the spin-polarized and non-spin-polarized cases. Our results reveal that the magnetic system exhibits significantly lower friction than the non-magnetic system, which can be explained by an electronic level mechanism of spins on friction properties. Additionally, this study provides an approach to estimate the spin friction under the formwork of DFT.