According to the actual working conditions, the rig derrick vibration model is established and the dynamic load is obtained by testing experiments. Transient response analysis is made on K-type drilling rig derrick with ANSYS software, the results indicate that the variation of each part of the rig derrick has the character of simultaneity under the effect of dynamic load, yet the moments to achieve maximum value is different, which shows the lag of derrick response. The derrick is mainly on up-down vibration with a certain degree of torsion vibration. Displacement occurs mainly on the top of the derrick, while the torsion amplitude decreases gradually from top to bottom. The largest vibration displacement 108.33mm, the maximum bending moment 80990.8N·m and the maximum stress -0.16354E 09Pa satisfy the design requirements respectively. In the process of the transient vibration, torsion vibration attenuation is rapid; while X direction decay is the fastest among X, Y and Z directions, which is consistent with the actual situation. Therefore, the transient analysis on derrick by using the actual dynamic load provides reference basis for the derrick structure design and safety assessment.