Aluminum alloy and low carbon steel plates are joined by self-piercing riveting,in which aluminum alloy plate is used as upper plate and low carbon steel plate is used as lower plate,respectively. The variation of the geometric characteristics of joint cross section with riveting force is observed and analyzed. When the riveting force increases,the bell-mouth diameter,rivet leg expansion and amount of undercut of the joint increase,while the lower plate raised height and bottom angle margin of the joint reduce. In the range of 16 ～24 kN riveting force,the bottom thickness of the joint varies slightly;when the riveting force is over 24 kN,the bottom thickness suddenly reduces as the riveting force increases. The results show that the shear load of the joint increases first and then decreases as the riveting force increases,and the maximum shear load reaches about 5.88 kN when the riveting force is 24 kN.