  A Guide Tube Calibration System (GTCS) has been designed for the Jiangmen
Underground Neutrino Observatory (JUNO), in order to measure the detector
energy response near the outer radius of the active volume. Recently, the
system has been constructed and tested, and the calibration algorithm has also
been studied to evaluate the risk when the simulation tuning is failed. In this
paper, we will report its construction and the performance tests in the lab.
Then the dependence of GTCS calibration model will be discussed to make sure
the algorithm is qualified, even if the inconsistency between simulation and
experimental data happens.
