High frequency filters are important components in microwave facilities application. With miniature volume, high performance and integratability, MEMS microstrip filter can significantly improve performance of Radio frequency system. By calculating chebyshev coupled microstrip bandpass filter design scheme, Threshold values of MEMS microstrip substrate parameters are defined to analyze dimensions variation property of MEMS microstrip filter relates with substrate parameters. Selection principle of substrate parameters for MEMS microstrip filter is presented, which indicates thickness and relative dielectric constant of substrate should not exceed the threshold values. The principle of threshold values can be applied as a guide on research and application of MEMS microstrip filter.