Phonon spectra of Cd1-xMnxS (x =0; 0.01; 0.05; 0.1; 0.15; 0.3) quantum dots (dsimilar to4.5 nm) are investigated by far-infrared reflection in the spectral range 80 - 600 cm(-1) and temperature range 80-300 K. The Cd1-xMnxS quantum dots have been synthesized by using aqueous solution precipitation. Together with the modes of (NaPO3)(6) surface active agent, and quantum dots CdS, we obtain a new mode of Mn at about 120 cm(-1). The position of this mode is discussed in the frame of the linear chain model with both mass and force constant defects.