Objective To explore the changes in diffusion kurtosis imaging(DKI)and diffusion tensor imaging(DTI)parameters and their relationship with cognitive ability in patients with mild traumatic brain injury(mTBI).Methods Forty-one mTBI patients(mTBI group)and 40 normal controls(normal control group)were examined by head MRI.Fractional anisotropy(FA),mean diffusivity(MD)of DTI parameters and mean kurtosis(MK),axial kurtosis(AK),radial kurtosis(RK),fractional kurtosis anisotropy(FKA),axonal water fraction(AWF),axial extra-axonal dispersion(AxEAD),radial extra-axonal dispersion(RadEAD)and tortuosity(TORT)of DKI parameters were calculated in region of interest(ROI).MMSE and Montreal cognitive assessment(MoCA)were used to evaluate the cognitive ability of the two groups.Results Compared with those in normal control group,AK in all lesion areas in mTBI group were increased,AWF,RK,AxEAD and RadEAD,FKA,MK were decreased(all P<0.05).Compared with those in normal control group,FA of pontine,corpus callosum and posterior limb of internal capsule in mTBI group were significantly decreased(all P<0.05);MD of putamen,posterior limb of internal capsule and thalamus in mTBI group were significantly increased(all P<0.05).Pearson correlation analysis showed that FKA was positively correlated with MMSE score at enrollment(r=0.81,P<0.05)and MMSE,MoCA scores at 3 months of treatment(r=0.88,r=0.89;all P<0.05).FA was positively correlated with MoCA score at enrollment and 3 months of treatment(r=0.82,P<0.05;r=0.76,P<0.05).MK was correlated with MMSE and MoCA scores at enrollment(r=0.77,r=0.76;all P<0.05)and 3 months after treatment(r=0.90,r=0.90;all P<0.05).MD was positively correlated with MMSE score at 3 months after treatment(r=0.90,P<0.05).Conclusion DKI combined with DTI can determine the degree of lesion by reflecting the changes of brain tissue microstructure,and is positively correlated with the cognitive ability of TBI patients.