Based on the finite-difference time-domain (FDTD) method, two kinds of terahertz line grid polarizers with enhanced line structures are designed to eliminate the influences of gravity and air disturbance on the performance of polarizers. The polarizers are fabricated by femtosecond laser micro-machining. The performance of polarizers is measured by time-domain terahertz spectroscopy and is compared with that of a commercial line grid polarizer. It is found that the transmittance of the polarizers is consistent with FDTD results. The degree of polarization and extinction ratio of the polarizer with discontinuous enhancement lines are better than that of commercial line grid polarizers.