The 20Ne(p,gamma)21Na is the first reaction of the NeNa cycle and having the slowest reaction rate it controls the speed of the entire cycle. The rate of the 20Ne(p,gamma)21Na reaction, depending on the temperature, is dominated by the high energy tail of a sub-threshold state at E_R = -6.7 keV, a direct capture component and a narrow resonance at E_R = 366 keV. In the next months LUNA at Laboratori Nazionali del Gran Sasso, will study the resonance and measure the cross section below 400 keV. The experimental approach and the study of the reaction using Monte Carlo simulation will be presented
