The 6—7 MeV quasi-monoenergetic pulsed γ -rays were produced on the FLASH Ⅱ accelerator. The pulsed γ -rays were generated via intense pulsed high power proton beam striking F target and measured with the 19 PIN semiconductor detectors and ST401 plastic scintillators. The yield of the quasi-monoenergetic pulsed γ photons from the 19F ( p

αγ ) 16 Ο reaction was calculated. By placing the target far enough downstream so that the time-of-flight was greater than the duration of the diode bremsstrahlung pulse

the quasi-monoenergetic pulsed γ -rays were discriminated from the diode bremsstrahlung

and the bremsstrahlung was depressed due to extending the distance between detector and diode. The quasi-monoenergetic pulsed γ -rays and their time delay were measured with ST401 plastic scintillator photomultiplier and the PIN semiconductor detector at various transmission distances. The proton energy at the beam current peak time was calculated by time-of-flight method. It is demonstrated by a series of experiments that the Cu

Cr

stainless steel target and the impurity in the target would not produce γ -ray interferences with other energies.