In this study, the effects of refining on the structure of sheet formation were investigated with three conditions of refined never-dried pulp fibres, and two different drying methods. The evaluations of morphological changes of fibres and its paper structure during refining were carried out by measuring WRV, sheet density, air permeability, light scattering coefficient, tensile strength, bonding index, zero-span tensile strength. After refining, the water retention values, available to evaluate the cell wall structure of fibre were increased; the sheet density, air permeability and light scattering coefficient, referred to sheet formation, were improved; the tensile strength and bonding index, referred to fibre bonding ability, were increased.