Field crop evapotranspiration (ETc) plays a key role in energy and water balance of agricultural systems， and the estimation of ETc under the sand-gravel mulching conditions is vital for assessing the influences of sand-gravel mulching on field crops. In order to accurately estimate the evapotranspiration of winter wheat under the conditions of sand-gravel mulching, the dynamic observation system of the lysimeter under a rain shelter was established in Yangling, Shaanxi. The FAO-56 Penman-Monteith equation was used to calculate the reference crop evapotranspiration (ETo). A weighing lysimeter was used to measure actual ETc of winter wheat under the different sand-gravel mulching amounts. The single and dual crop coefficient approaches were adopted in conjunction with ETo to estimate measured ETc. The results showed that a good linear relationship was obtained between single crop coefficient and sand-gravel mulching amounts at the three different growth stages of winter wheat. The equation can better simulate ETc of winter wheat under the sand-gravel mulching conditions. The ranges of determination coefficient (R2) between measured ETc and ETcS (ETc estimated by the single crop coefficient method) were 0.77~0.80 (in the first year) and 0.73~0.76 (in the second year), respectively. There was a good linear relationship between dual crop coefficient and sand-gravel mulching amounts. This relationship was introduced to modify the dual crop coefficient under sand-gravel mulching conditions. The modified dual crop coefficient approach can also better simulate ETc of winter wheat under different sand-gravel mulching amounts compared with the measured ETc. The ranges of R2 between the measured ETc and the simulated ETc were 0.83~0.88 (in the first year) and 0.87~0.92 (in the second year), respectively. The single crop coefficient approach simulated average evapotranspiration better than the dual crop coefficient approach, although the dual crop coefficient approach was more accurate on daily ETc. In conclusion, the single and dual crop coefficient approaches were still applicable for estimating the ETc of winter wheat under the sand-gravel mulching conditions, but it needed revision by using the measured data.