Because the spatial virtual axis does not exist as a direct substantiality,the traditional technique of contact measurement can not be adopted for it. Therefore,the research on the measurement instance of virtual boresight of satellite-borne camera was carried out by using normal instrument to derive it according to its optical characteristics. Every object for transfering attitude relations was modeled based on measurable data. According to the internal relevance between every object,the precise formula of spatial virtual axis is deduced. Because of the considerate design for the existing conditions,the technique can be applied to the engineering practices.