The reflection, absorption and transmission characteristics of a terahertz waves (T-rays) in a bounded plasma slab with high collision frequency and high plasma density are studied in this paper. The method of impedance transformation with multiple dielectrics is used to describe the propagation of THz waves in the plasma layer. The effect of various plasma parameters such as the plasma number density, sheet thickness, wave frequency and collision frequency on the power transmission, absorption and reflection is investigated. The results of numerical calculation show that a THz wave can transmit though a dense and high collision frequency (THz) plasma with reflectionless and absorptionless power. When the change of plasma density leads the plasma frequency to be in the vicinity of the incident THz wave frequency, the plasma can absorb the most THz wave power. The potential applications of these propagation properties are discussed in this paper.