An algorithm for the decision of the automatic filter based on the uniform standard is proposed for the numerical analysis of the spatial carrier-fringe signal. At first, a numerical simulation is presented to demonstrate the feasibility and validity of the proposed algorithm. It is shown that the proper selection of the spatial filter would improve the quality of the reconstructed image. However, the distribution of the spectrum varies with different objects. It means that, there is not a deterministic function for the description of the distribution of the spectrum. Therefore, it brings difficulties to define a precise spatial filter. According to the numerical analysis of the distribution of the spectrum of each spatial carrier-fringe signal, the uniform standard for the decision of the threshold of the adaptive filter is researched, which helps the automatic spatial filtering method to be more advantageous for the dynamic and automatic analysis. The detailed steps and an example of 3-D shape measurement are presented.