The effect induced by the increment of refraction index and dispersion of glass in the wide bands FT(Fourier Translate) lens were introduced.The formula of the increment of secondary spectrum which brought by the increment of refraction index and dispersion of glass were deduced.The increment of secondary spectrum of thin double lens in wide bands system was emphatically discussed.In this thesis,the coefficient of the increment to secondary spectrum is 0.28,which is said this increment is about 28% of the theory secondary spectrum of thin double lens,so it should not be ignored by any designer.The example showed in this thesis indicated that the increment of refraction index and dispersion of glass in the wide bands system had more serious effect to its imaging quality.In addition,the FT lens wavefront aberrations were mentioned,and the wavefront aberrations were designed less than 1/10 waves in the using bands.When the best glasses couple were used to produce the FT lens,the wavefront aberration could be rem