We present a refined muon identification algorithm for the LHCb experiment suitable for the first period of data taking. The new algorithm is robust against possible inefficiencies of the Muon Detector and takes properly into account the momentum dependence, so it can be tuned with calibration samples and exported to signal samples with different momentum spectra without large corrections. The average performance depends on the momentum spectrum of the analyzed sample: with the current simulation we find for tracks with p > 3 GeV/c in a generic b-inclusive sample a muon identification efficiency of 90 % for a misidentification rate of hadrons and electrons of ~2.4 % (~ 1 % excluding pi's and K's decays in flight). Additional rejection power can be obtained by combining in a proper way the informations coming from all the other subdetectors in a global Likelihood: in this case for a muon identification efficiency of 90 % we find a misidentification rate of ~1.8 % (~ 0.8 % excluding pi's and K's decays in flight
