In a capillary discharge experiment for the neon-like argon lasing, we have proposed an experimental scheme to verify that the multi-spike of X-ray diode (XRD) signal is a multi-pulse laser or is a reflection of the laser pulse in the XRD. The ceramic capillary has an inner diameter of 3 mm and a length of 200 mm. At the gas pressure of 28 Pa and discharge current of 27 kA, stable lasing has been realized. The experimental results prove that the multi-spike of XRD signal is a reflection of the electromagnetic signal produced by the laser pulse in the XRD. The improved electrocircuit scheme of the XRD to minimize the reflection phenomena is also found.