Abstract: This paper aims to investigate the influence of different temperature boundary conditions on the decoupling mechanism of the Mach number effect and thermodynamic effect in compressible wall-bounded turbulence, in order to more accurately evaluate the drag characteristics of compressible channel turbulence. Based on direct numerical simulations, this study comparatively analyzes the statistical characteristics of compressible channel turbulence under two conditions: constrained bulk cooling (CBC) and zero bulk cooling (ZBC), at bulk Mach numbers of 0.3, 0.8, and 1.5, and a bulk Reynolds number of 3000. The results indicate that compared to the ZBC condition, the CBC condition effectively isolates the interference of thermodynamic effects on the flow field, significantly weakening the influence of the Mach number on turbulence statistics. This leads to a decrease in the peak streamwise mean velocity by 15% at the same Mach number and effectively suppresses the relaminarization phenomenon prone to occur at high Mach numbers. Under the CBC condition, the variation amplitude of the skin friction coefficient is milder compared to the ZBC condition, yet it remains significantly influenced by the non-adiabatic parameter \mathit\Theta . Specifically, when this parameter decreases from 1.0 to 0.5, the wall temperature drops accordingly, and the wall heat flux is reduced by nearly 40%, resulting in a nearly 12% reduction in viscous shear stress in the near-wall region. Furthermore, the CBC condition significantly reduces the sensitivity of the drag coefficient to the Reynolds number. When the Reynolds number increases by 60%, the relative variation in the drag coefficient is less than one-third of that observed under the ZBC condition, indicating that the momentum transport mechanism of the flow field is more stable under the constrained bulk temperature.