The invention provides a green synthesis method of a germanium quantum dot in a solution, a germanium quantum dot and application thereof in biological imaging. The green synthesis method comprises the following step: by taking germanium dioxide as a germanium source, polyvinylpyrrolidone as a protective agent and sodium borohydride as a reducing agent, preparing to obtain the germanium quantum dot. According to the invention, the used raw materials are simple, accessible and stable in property, and basically has no biological toxicity; high temperature and protection of inert gas are not required in the reaction process, thereby ensuring that the green synthesis method is simple and easy to operate; the prepared germanium quantum dot having blue fluorescence has a quantum yield of 26% or above, can be easily separated from the system, has no cytotoxicity and can be well used in biological cell imaging.