Forward extrusion experiments of as cast AZ31 magnesium alloy were carried out at different temperatures and different extrusion ratios using the homogenised and non‐homogenised billets. The elongation of pre‐ and post‐extrusion of the two different initial state billets were investigated. Experimental results show that elongation will increase when the as cast AZ31 magnesium alloy is treated by homogenising. Regardless of whether the billets are treated by homogenising, the elongation of post‐extrusion is improved compared with that of pre‐extrusion. The elongation of post‐extrusion using the homogenised billet is higher than that of the non‐homogenised one.