After using the strict solution of phase difference DF based on short-baseline array derives the function relationship between phase shift and Doppler shift, the analysis formula of signal wavelength is derived by measuring for phase difference and radiation frequency. Whereafter, the analysis formula is predigested by comparing and combining equivalent item. The error analysis for reduced form equation shows that the wavelength measurement error obtained by new method based on short-baseline phase difference measurement may be less than 1 mm when the measurement error for measured frequency is larger than several megacycles for decimeter wave signal. This may be best method which can apply to engineering design up to the present