The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field.It is found that the excitation energies and absorption spectra of zigzag tubes (11,0) and (10,0) show opposite trends with the strain under the action of the magnetic field.For the (11,0) tube,the excitation energy decreases with the increasing uniaxial strain,with a splitting appearing in the absorption spectra.For the (i0,0) tube,the variation trend firstly increases and then decreases,with a reversal point appearing in the absorption spectra.More interesting,at the reversal point the intensity of optical absorption is the largest because of the degeneracy of the two bands nearest to the Fermi Level,which is expected to be observed in the future experiment.The similar variation trend is also exhibited in the binding energy for the two kinds of semiconducting tubes.