Ho3+-Tm3+-codoped GeS(2)-Ga(2)S(3)-CsCl chalcohalide glasses are prepared and their upconversion (UC) show that the green UC luminescence from Ho3+ ions under an 808 nm diode laser excitation is considerably enhanced by Tm3+ ions codoping while the red UC luminescence from Tm3+ ions is weakened. The relevant mechanism is analyzed with respect to the energy transfer mechanism from Tm3+ ions to Ho3+ ions due to some energy levels of the Ho3+ ions is close to that of the Tm3+ ions.