Abstract: To reduce the large computation of joint direction-of-arrival (DOA) and polarization parameters estimation based on polarization sensitive linear array, a reduced-dimensional Root-MUSIC with the modulus constraint is proposed. The algorithm in this paper estimates the DOA and polarization parameters in two separate steps. In step one, DOA parameter is separated from polarization parameters and estimated by Root-MUSIC algorithm; in step two, cost function is constructed according to modulus constraint and polarization parameters are obtained with closed-form formulas. Compared with the traditional MUSIC algorithm, the algorithm in this paper avoids the spectrum peak search, and greatly improves the operation efficiency. Compared with the ESPRIT algorithm, this algorithm avoids parameters matching problem. The computer simulation results verify the correctness of this algorithm, and as well as its high success rate and precision of the angle estimation. When the incident angles of two target signals are close, it also can distinguish the two signals very well.