Microalgae are recognized as promising feedstocks for biofuel production and have been intensively studied. However, a systematic investigation of the relationship between cellular components and fuel properties in microalgae is currently absent. This review introduces recent advances in microalgal torrefaction and critically evaluates the properties of torrefied products from the viewpoint of molecular conversion. We also critically review how to regulate biosynthesis to better modulate microalgal metabolism and how cellular components impact fuel properties. Process optimization to improve solid fuel properties using different torrefaction technologies are furthermore comprehensively compared and summarized. This review provides new insights into developing innovative microalgal solid biofuels and increasing their commercial viability.