Reasoning about assembly sequences is useful for identifying the feasibility of assembly sequences according to the assembly knowledge. Technologies used for reasoning about assembly sequences have crucial impacts on the efficiency and automation of assembly sequence planning. Description Logic (DL) is well-known for representing and reasoning about knowledge of static application domains; it offers considerable expressive power going far beyond propositional logic while reasoning is still decidable. In this paper, we bring the power and character of description logic into reasoning about assembly sequences. Assembly knowledge is firstly described by a description logic enhanced with some rules. Then, the feasibility of assembly operations is decided by utilizing the reasoning services provided by description logics and rules. An example has been provided to demonstrate the usefulness and executability of the proposed approach.