Personalized theranostics of cancer is increasingly desired, and can be realized by virtue of multifunctional nanomaterials with possible high performances. Gold nanoparticles (GNPs) are a type of especially promising candidate for cancer theranostics, because their synthesis and modification are facile, their structures and physicochemical properties are flexibly controlled, and they are also biocompatible. Especially, the localized surface plasmon resonance and multivalent coordination effects on the surface endow them with NIR light-triggered photothermal imaging and therapy, controlled drug release, and targeted drug delivery. Although the structure, properties, and theranostic application of GNPs are considerably plentiful, no expert review systematically explains the relationships among their structure, property. and application and induces the engineering rationales of GNPs for cancer theranostics. Hence, there are no clear rules to guide the facile construction of optimal GNP structures aiming at a specific theranostic application. A series of structural-engineering rationales of GNPs for cancer theranostics is proposed through digging out the deep relationships between the structure and properties of GNPs. These rationales will be inspiring for guiding the engineering of specific and advanced GNPs for personalized cancer theranostics.