Abstract: Uncertainty of measurement results of tillage depth of rotary tiller was evaluated.Sources and influence factors of uncertainty of measurement results were analyzed，and expanded uncertainty was obtained.Results showed that average of tillage depth of rotary tiller x=15.795 cm，coverage factor k=2，and expended uncertainty U=0.111 cm.Uncertainty component introduced by repeatability of measurement had a great influence on uncertainty of measurement results in measurement of tillage depth of rotary tiller.