Based on energy dispersion relation of the deformed single-walled carbon nanotubes （SWCNTs）, various curves of the electronic velocity and effective mass of the lowest conduction band versus deformation parameters for SWCNTs are computed. It is found that only when a deformation occurs in the special direction（s） and is limited to a region of low deformation （the deformation parameter ε≤002）, the variations of the electronic average velocity vmean and average effective mass m*mean of different types of SWCNTs are very small （the relative variation≤2%）, which suggests that in these cases the electronic transport properties for SWCNTs under a low bias are basically stable. Whereas in other cases the electronic average velocity, or electronic average effective mass, or both of them vary significantly, even change in a dramatic way. This means that the electronic transport properties for SWCNTs under a low bias are unstable, even extremely unstable.