Based on the spatial phase delay of beams, a displacement measurement method is proposed for homodyne interferometers. In this method, two detectors are arranged in the interference spot to collect signals. Based on the algorithm of least squares fitting the parameters of the ellipse equation, the relative phase of the signals is solved to calculate the displacement. The proposed method uses optical fiber bundles for beam reception, which is more compact in structure than the traditional quadrature phase calculation method, and eliminates polarization mixing. The spatial delay phase in the method can be any unknown constant, which makes it more applicable in practice. The feasibility of this method is verified by ZEMAX simulations and experiments. The experimental results show that the 3σ of errors without the effect of power noise and vibration is 7.2 nm.