The combustion characteristics and thermal behavior of modified double base propellant containing Trans-1, 4, 5, 8-tetranitro-1, 4, 5, 8-tetraaza dacalin (TNAD) were investigated by burning rate test and PDSC. Results show that there was a general increase(greater than 9%) in burning rate when RDX is replaced by TNAD in propellant in the tested pressure range of 9-22 MPa. The pressure exponent in the pressure range of 9-15 MPa decreases from 0.26 to 0.18, but increases from 0.10 to 0.14 when the pressure is above 15 MPa. By analyzing from PDSC data, it is suggested that there is a strong interaction between NC/NG and TNAD, which increase the burning rate of propellant by enhancing the decomposition rate and heat release of the mixed system.