The utility model discloses a testing device for in situ testing of roadbed compaction. The testing device comprises a long rod penetration instrument and a triangular frame assembly. The long rod penetration instrument is installed on the triangular frame assembly and comprises a guiding rod, a hammer pad and a penetration rod. The guiding rod is arranged above the penetration rod, a thread is arranged at the lower end of the guiding rod, the lower end of the guiding rod stretches in the hammer pad and is in threaded connection with the upper portion of the hammer pad, a hollow groove is formed in the lower portion of the hammer pad, and the upper end of the penetration rod stretches in the hollow groove and is in close fit with the hollow groove. A clamping head is fixed to the upper end of the guiding rod, the guiding rod is sleeved with a hammer, the hammer is located between the clamping head and the hammer pad, the bottom of the hammer is in a semispherical shape, a groove matched with the bottom of the hammer is formed in the upper portion of the hammer pad, a penetration hammer is fixed to the lower end of the penetration rod, and scale lines are arranged on the penetration rod. According to the testing device, under the condition that the measuring precision is ensured, the measuring efficiency can be improved, the personnel allocation amount can be reduced, and in situ testing for the fine-grained soil roadbed compaction can be effectively, accurately and rapidly conducted.