The invention provides a quantitative description method for an assembly based on a spatially connected framework. The spatially connected framework is established according to the positions of partsin the assembly, the position of a mating surface and a connection relationship, a shortest path distance between any two parts in the framework is calculated based on the framework, finally the surface point random sampling is carried out on the any two parts in the assembly, Euclidean distances between the two random points and the respective parts and a sum of framework path distances between the two parts are calculated, and distance distribution vectors among all parts in the assembly are counted to complete the quantitative description of the assembly in the form of a vector matrix. According to the method, spatial position information, connection relationship information and model shape information are integrated in an European space and represented, and assembly information is aggregated into an information descriptor in a matrix form by statistical means. The descriptor has translational rotation invariance and is only affected by a model under the condition of ensuring accuracy, the information storage form is simple, and the assembly information can be accurately expressed.