In order to support unmanned production at night and extend to 24 hour unmanned production, we proposed the introduction of off-line robots, As part of the work for the realisation of this concept, the operational analysis of the off-line robots in a cellular assembly shop is carried out in this paper. First, a stochastic analysis is made to determine the optimal number of assembly cells for each off-line robot, and factors affecting the optimal number are investigated by practical examples. Next, two methods of determining the optimal service sequence for the off-line robot are investigated, and finally a comparison between the two methods is made.