We experimentally demonstrate the quantum anti-Zeno effect in a two-level system based on a single trapped ion 40Ca+.In the large detuning regime,we show that the transfer from the ground state to the excited state can be remarkably enhanced by the inserted projection measurements.The inserted measurements in our experiment are realized by the electron shelving technique.Compared to the ideal projection measurement,which makes the quantum state collapse instantaneously,a practical electron shelving process needs a finite time duration.The minimum time for this collapse process is shown to be inversely proportional to the square of the coupling strength between the measurement laser and the system.