High-density and high-thermal-stability alkyl diamondoid fuels have drawn tremendous attention since they can provide more propulsion energy and remove excess heat for aerospace vehicles. Recent progress on synthesis of alkyl diamondoid fuels via rearrangement and alkylation is summarized in this review. Proposed rearrangement pathway is put forward by density functional theory calculation and reaction results. Also, regioselective synthesis of alkyl diamondoids with specific alkyl group (methyl, ethyl, propyl, butyl) is conducted via alkylation of adamantane derivatives. The performance of alkyl diamondoid fuels is highlighted including density, low-temperature performance and especially thermal stability, and correlated with the hydrocarbon structure. The compact structure with short alkyl substituents and more rings of carbon leads to a high density, while the low-temperature performance is dependent on the symmetry of molecular structure. The thermal stability is mainly related to the type of carbon contained in the molecule structure, in the order of quaternary carbon > primary carbon > secondary carbon > tertiary carbon. Through the regioselective and high throughput synthesis method which is expected to be applied in the future, the alkyl group can be orientatedly substituted on the tertiary carbon atom of the adamantane core, and then converted to the quaternary carbon atom, improving thermal stability while maintaining higher density of alky diamondoid.