Abstract: This paper studies the reliability of non-series CIMS production line. By using the method of an equivalent workstation, a theorem on availability of buffers is proposed. In steady state, a non-series CIMS system, such as an assembly line and disassembly line, can be solved through transformation into a series system. Additionally, analysis of a sufficient condition and several necessary conditions for not losing any workpieces during operation is given. Finally the curve of P-k-K is shown to hint the probable scope of available solution to a real problem.