Several industrial- and research-type hydroxyl-terminated polybutadiene (HTPB) composite solid rocket propellants, containing dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) particles and, featuring the same nominal composition, were prepared. The energetic properties of composite propellants containing different mass fractions of TKX-50 particles were theoretically computed and experimentally evaluated. The effects of different mass fractions of TKX-50 on the rheological properties of both TKX-50/HTPB binder slurries and AP/HTPB/Al propellant slurries were investigated. The strand burning rates, the associated combustion flame structures, and the hazardous properties of the resulting propellants were experimentally analyzed. All of the properties mentioned above were also compared to those of the reference propellant without TKX-50. The results show that the prepared TKX-50 particles can sufficiently be dispersed in the HTPB binder plasticized by di-2-etylhexyl sebacate (DOS). The propellant compositions containing different mass fractions of TKX-50 are insensitive to impact and friction, differentlyfrom the reference propellant without TKX-50. Moreover, over the explored pressure range, TKX-50 can affect the combustion behavior and decrease the burning rate as well as pressure exponent of composite solid propellants compared with the reference composition.