Density is one of the most important thermophysical properties of aviation fuel for the advanced fuel-cooled thermal management. The density of a hydrocarbon fuel JP-10 was measured using a gamma-ray radial method calibrated with deionized water, cyclohexane, and a mixture of n-heptane and n-octane. The average absolute deviation (AAD) of deionized water is 0.22% under 3.0 MPa and 0.43% under 5.0 MPa, that of cyclohexane is 0.80% under 5.0 MPa, and that of the mixture of n-heptane and n-octane is 0.33% under 5.1 MPa. The experimental density of JP-10 was reported at 267 to 873 K under the pressure of 0.70 to 6.00 MPa. Two empirical correlations were used to fit the liquid and gas density data separately. The results are that the AAD for all the liquid data is 0.46%, and that for all the gas data is 6.12%. Finally, the isobaric thermal expansion was calculated.