Two varieties, Yuexinzhan and Guangchao 3, were used to study leaf thickness in rice in this experiment. The thickness of the leaf blade was measured by the nondestructive leaf thickness instrument, which was modified from the thickness instrument for steel objects (John Bull, England). The contacting area between the leaf and the probe of the instrument was 0.5 cm2. There was no significant difference between the thickness of steel materials measured by the nondestructive rice leaf thickness instrument and the micrometer. The correlation between the thickness of the rice leaf blade measured by the nondestructive rice leaf thickness instrument and the specific leaf weight (SLW) was significant (P ＜ 0.05 or P ＜0.01). The results also showed that the rice leaf thickness was uneven and asymmetric. The thickness and SLW of flag leaf tended to increase from the base to the tip of the leaf blade. The middle part of the second and third top leaf was the thickest, but no significant difference in thickness between the basal part and the fore part was found. Drawing a line on the main vein in the top three leaves, the left part was thinner than the right part. The thickness of the lower leaves (6/0-9/0) on the main culm tended to increase with increasing positions of the leaves in the early and middle stages, but the tendency was not the same for the higher leaves (10/0 upwards), although the higher leaves (10/0 upward) were thicker than the lower leaves (9/0 or downward). Furthermore, different CO2 concentrations (550 ± 30, 460 ± 30 μmol mol-1) in the growth boxes had no effect on the thickness of rice leaf blades. It can be concluded that the measurement of rice leaf thickness using the nondestructive rice leaf thickness instrument is simple, precise, and nondestructive.