The x-ray optical properties of X-Ray Telescopes (XRTs) on board Asca were evaluated with an x-ray pencil beam at ISAS 30 m x-ray beam line. The total effective area of four XRTs is obtained to be about 1300 cm2, 800 cm2, and 450 cm2 at each energy of 1.5 keV, 4.5 keV, and 8.0 keV, respectively. These values are about 15% less than those calculated by ray tracing method in an ideal case. The shadow effect of closely packed foils might be the main reason for the degradation of effective area. The Point Spread Function of XRT was also measured by an x-ray CCD. We have also measured the contamination of stray light, which were caused by the one time reflected photons (by primary or secondary mirror) and photons reflected on the back side surface of the mirror shells. The stray light profile and intensity were consistent to the results simulated by the ray tracing.