We propose several new methods to calculate threshold and power for Quantitative Trait Locus (QTL) detection. They are based on asymptotic theoretical results presented in Rabier et al. (2009) . The asymptotic validity is checked by simulations. The methods proposed are fast and easy to implement. A comparison of power between a multiple testing procedure and a global test has been realized, showing far better performances of the global test for the detection of a QTL