Recycling in the HT-6M tokamak is studied by changing the working gas from deuterium to hydrogen and vice versa. Spectroscopic technique (Balmer lines) is used to follow the change of the relative concentration of the plasma. The results show that the reflection coefficient near the wall is about 0. 59, and in the plasma of the first discharge after a gas change, the wall-released isotope amount to 65% .The recyclingc mechanism in the HT-6M tokamak is discussed.