The invention relates to the technical field of polymer melt spinning key equipment, in particular to a residence time controllable melt spinning assembly, comprising an outer casing with an inner cavity; a transitional plate is arranged in the upper portion of the inner cavity, a spinneret plate is arranged at the lower end of the inner cavity, a sand cup is arranged between the transitional plate and the spinneret plate, and is provided with a sand cavity with an upper opening, a gland which is changeable is arranged at the upper opening of the sand cavity, and the volume of the sand cavityis regulated according to different degree of protrusions of the bottom surfaces of the different glands facing the inside of the sand cavity. The gland which is changeable is matched with the sand cavity so that the sand cavity can have different volume. When the spinning assembly is used for spinning fibers in different fiber number, the volume of the sand cavity can be increased or decreased doubly flexibly, the residence time of a melt in the sand cavity can be regulated effectively, and thus, degradation of the melt can be decreased remarkably and the purpose of smooth spinning is achieved.