Plate structures are widely used in acoustical insulation design, their critical frequency and coincidence frequencies are closely related to sound radiation and sound insulation performance of plate structures. From the mechanism of coincidence effect and conditions to cause coincidence effect, based on the vibration control equation of thin plates made of saturated porous materials, the calculation formulas for critical frequency and coincidence frequency of thin plates made of saturated porous materials were deduced through theoretical analysis. Using numerical examples, the parametric analysis for coincidence frequency and critical frequency of thin plates made of saturated porous materials were performed. The variation laws of coincidence frequency with changes of plate thickness, porosity, incident angle, and permeability coefficient were analyzed. The coincidence frequencies of thin plates made of saturated porous materials under different porosities were compared with those of elastic solid plate with changes of plate thickness and incident angle. Results showed that coincidence frequencies of single-phase elastic solid plates are much larger than those of thin plates made of saturated porous materials, their coincidence frequencies decrease with increase in plate thickness and incident angle, and increase with increase in porosity, while permeability coefficients almost have no effect on their coincidence frequencies.