A clamping device for a bicycle carry rack, comprising: a tube , a first clamp unit , a second clamp unit and a fastening unit , the first clamp unit and the second clamp unit respectively located on two ends of the tube , an end member connected to one end of the tube ; the fastening unit having a pin which includes a head and a threaded end respective formed on two ends thereof, the pin extending through the first clamp unit , the tube , a spring , the second clamp unit and threadedly connected to a knob by the threaded end , the spring connected to the second clamp unit , the fastening unit connected between the first and second clamp units , and the first clamp unit being a C-shaped unit and including a clamping slot and an entrance which communicates with the clamping slot , a notch defined in the first clamp unit and communicating with the entrance , the clamping slot of the first clamp unit adapted to clamp a frame of a bicycle carry rack via the entrance , a pivotal portion formed in the first clamp unit and transversely located below the clamping slot , the first clamp unit being pivotable about the pivotal portion , a receiving groove defined in the first clamping unit , a contact portion formed between the clamping slot and the receiving groove , a restriction recess defined in the first clamp unit and located opposite to the receiving groove , and the head removably located in the restriction recess , the clamping device being characterized in that the spring is separated from the end member by clamping the second clamp unit , and the tube travels a distance so that the head on the pin is separated from the restriction recess , the first clamp unit is pivoted and the contact portion contacts the tube , the clamping slot is adapted to clamp the frame of the bicycle carry rack via the entrance , and the pin is engaged with the notch , the second clamp unit is released to force the head on the pin to be engaged with the restriction recess . a tube , a first clamp unit , a second clamp unit and a fastening unit , the first clamp unit and the second clamp unit respectively located on two ends of the tube , an end member connected to one end of the tube ; the fastening unit having a pin which includes a head and a threaded end respective formed on two ends thereof, the pin extending through the first clamp unit , the tube , a spring , the second clamp unit and threadedly connected to a knob by the threaded end , the spring connected to the second clamp unit , the fastening unit connected between the first and second clamp units , and the first clamp unit being a C-shaped unit and including a clamping slot and an entrance which communicates with the clamping slot , a notch defined in the first clamp unit and communicating with the entrance , the clamping slot of the first clamp unit adapted to clamp a frame of a bicycle carry rack via the entrance , a pivotal portion formed in the first clamp unit and transversely located below the clamping slot , the first clamp unit being pivotable about the pivotal portion , a receiving groove defined in the first clamping unit , a contact portion formed between the clamping slot and the receiving groove , a restriction recess defined in the first clamp unit and located opposite to the receiving groove , and the head removably located in the restriction recess , the clamping device being characterized in that the spring is separated from the end member by clamping the second clamp unit , and the tube travels a distance so that the head on the pin is separated from the restriction recess , the first clamp unit is pivoted and the contact portion contacts the tube , the clamping slot is adapted to clamp the frame of the bicycle carry rack via the entrance , and the pin is engaged with the notch , the second clamp unit is released to force the head on the pin to be engaged with the restriction recess . <EOS>