Clamping tweezers include two elastic arms, two grips, and an adjustment block. The two elastic arms are connected to each other at one end to form a connected end, and start to open from the connected end. Each elastic arm defines a number of spaced grooves adjacent to the connected end. The two grips are rotatably positioned on the distal ends of the two elastic arms, and include two gripping surfaces that face to each other. The adjustment block fits over the two elastic arms from the connected end, and includes teeth and an elastic piece configured for allowing the teeth to engage with the grooves. The adjustment block is able to slide along the elastic arms to adjust an open angle of the two elastic arms.