Abstract: The macroscopic morphology, transverse morphology, microstructure and mechanical properties of the friction stir lap joints of 1 mm thick TA2-M pure titanium were investigated by varying the welding speed while the keeping the other welding parameters constant. The results show that as the welding speed increases from 60 mm/min to 150 mm/min, the weld core area in the joint cross-section exhibits a“bowl” structure; compared with the base metal (BM), the grains in the heat-affected zone (HAZ) grow significantly, and their sizes show different degrees of inhomogeneity. Due to the heat generated by the friction of the stirring head, some grains undergo abnormal growth and morphological changes. As the welding speed increases, the grains undergo a short dynamic recrystallization process in the stirring region. Since the crushed and recrystallized grains do not have enough time to grow, this results in finer and denser grains in the stirring region, especially in the stirred zone(SZ). Since the duration of high temperature in the welding process is too short, the phase transformation in the SZ is not significant, so the grains in the SZ become refined and densified. The microhardness curve of the joint presents "∧" type distribution, in which the hardness of the base material area is lowest, the average hardness in the weld core area and the tensile strength of the joint show a trend of first increase and then decrease with the increase of the welding speed. The joint welded at a speed of 75 mm/min exhibits the optimal microhardness, with a peak value of 250 HV. A large number of dimples with different sizes are observed on the fracture surface of the joint, including equiaxed and elongated ellipsoidal shear dimples, which show obvious plastic fracture characteristics and indicate that a 45° slip occurs in the joints during the tensile process.