Spin-dependent electroresistance (ER) was observed in polycrystalline Nd0.67Sr0.33MnOy (y=3.00, 2.95, 2.90, 2.85, 2.80) samples, which were synthesized by solid-state reaction. For the sample with stoichiometry y=3.0, the I-V characteristic shows ohmic linearity over the whole range of measuring temperature. For the samples with oxygen-deficiency, i.e. yI-V curve is linear when temperature is above a certain point, similar to the case of y=3.0. However, the electric resistance strongly depends on load current, decreasing remarkably with increasing current load when temperature falls below the critical temperature. For the sample of y=2.85, the ER ratio reaches 80% when the load current increases from 1 to 30 μA. The spin-dependent ER effect should be strongly related with the oxygen-deficiency and grain boundary effect.