We reported about an experiment aimed at verifying the statistical technique, which has been proposed first by Mikhail S. Belen'Kii to solve the tilt indetermination problem from the laser guide star(LGS) adaptive optics(AO) system. The tilt components of wave fronts were measured synchronously from a Rayleigh guide star by use of a 25-cm telescope as an auxiliary telescope and from a star by use of a telescope with a 1.2-m aperture at Yunnan Observatories. The result shown that the instability of the auxiliary telescope's tracking system is an important error source for the tilt measurement.