Abstract We propose a “multi-layer (ML)” 1D model for understanding behaviors of partially detached divertor plasmas. The basic idea is to analyze interaction among the adjacent flux tubes for the attached and detached states in the divertor region. Cross-field transport terms in both SOL and divertor regions are considered in this model. We show some preliminary simulations which indicate necessity of the ML 1D model. According to the simulations, cross-field energy flow in the divertor region can affect stability of a detachment front of partially detached plasmas, i.e. such flow can decrease the front speed towards the X point.