Abstract Synthesis of high-quality graphene layers on insulating substrates is highly desirable for future graphene-based high-speed electronics. Besides the use of gaseous hydrocarbon sources, solid and liquid hydrocarbon sources have recently shown great promises for high-quality graphene growth. Here, I report chemical vapor deposition growth of mono- to few-layer graphene directly on SiO2 substrate using ethanol as liquid hydrocarbon feedstock. The growth process of graphene has been systematically investigated as a function of annealing temperature as well as different seed layers. Interestingly, it was found that the carbon atoms produced by thermal decomposition of ethanol form sp2 carbon network on SiO2 surface thereby forming nanographene flakes via an intermediate carbon-based nanostructured state carbon nanotube. This work might pave the way to an understanding for economical and catalyst-free graphene growth compatible with current silicon-processing techniques, and it can be applied on a variety of insulating surfaces including quartz, sapphire, and fused silica.