The tensile properties of polyester warp knitted fabrics of satin and reverse satin structure with various lengths of underlap were studied. In the range of low tension, the satin warp knitted fabric showed larger tensile energy and elongation in the direction of $0^circ$ and larger tensile linearity, tensile resilience and initial modulus in $90^circ$. Meanwhile, reverse satin one showed larger initial moduli in 0$^{circ}$ and larger the others in $90^circ$. In the range of high tension, the tendencies of both fabrics in $0^circ$ direction were almost the same as those in all direction. As the under laps were shorter for both fabrics, tensile linearity, tensile energy and elongation increased, but tensile resilience decreased in all directions. However initial moduli were changed little.