The present invention discloses a multi-stage partial pressure type capillary tube rheometer, wherein the die assembly of the rheometer comprises a first material cylinder and a second material cylinder, the terminal end of the first material cylinder is provided with a cylindrical concave groove, the concave groove is concentric with the inner cavity of the first material cylinder, the diameter of the concave groove is greater than the diameter of the inner cavity, the top end of the second material cylinder is provided with a cylindrical boss, the boss is concentric with the inner cavity of the second material cylinder, the boss is matched with the diameter of the concave groove of the first material cylinder, the boss of the second material cylinder is inserted into the concave groove of the first material cylinder, the terminal end of the second material cylinder is provided with a cylindrical concave groove, the cylindrical concave groove is concentric with the inner cavity of the second material cylinder, a first die is arranged at the terminal end of the inner cavity of the first material cylinder, a second die is arranged at the terminal end of the inner cavity of the second material cylinder, and the first material cylinder is fixedly connected to the second material cylinder. With the multi-stage partial pressure type capillary tube rheometer of the present invention, the pressure at the inlet of the first die can be increased, and the viscosity of the polymer melt under different pressures in the single test can be achieved so as to substantially improve the experimental efficiency.