The invention provides a sampling NMOS tube and a generation method thereof, a voltage bootstrapping sampling switch and an analogue-digital converter. The sampling NMOS tube and the generation method thereof, the voltage bootstrapping sampling switch and the analogue-digital converter are applied to the field of analogue-digital converters. A diode D1 is added between the source of the sampling NMOS tube and a power source, while a diode D2 is added between the drain of the sampling NMOS tube and the power source; when the input voltage is added, as the input voltage generally is not greater than the power voltage, the diodes D1/D2 are reversely biased and the stray capacitance of the diodes is increased with the increase of the input voltage; meanwhile, as the input voltage is generally not lower than 0, parasitic diodes DP1/DP2 between the source/drain of the NMOS tube and the ground also are reversely biased and the stray capacitance of the two parasitic diodes are reduced with the increase of the input voltage; as a result, the change of the stray capacitance of the diodes D1/D2 along with the input voltage compensates the change of the stray capacitance of the parasitic diodes DP1/DP2 with the input voltage, so that the sampled capacitance does not change along with the change of the input voltage, and therefore, the linearity of the sampling switch and the linearity of the whole circuit are greatly increased.