The standard model of independent component analysis (ICA) and its assumptions,ambiguities,nongaussianity measures and general solution were introduced.A kind of fast ICA algorithm based on kurtosis was discussed.Then,A weak signal feature extraction algorithm for passive infrared spectra based on standard model of ICA was proposed.Comparison was made with difference spectra.Experimental results show that the proposed algorithm can effectively detect the weak signal form passive infrared spectra,and doesn′t depend on background spectra.