The invention provides a time interval measurement system and measurement method of adopting a mixed interpolation cascade structure. The system comprises a main portal generation, an error extractionunit, a clock unit, a rough measuring unit, a first simulation interpolation unit, a second simulation interpolation unit, a first figure interpolation unit, a second figure interpolation unit and anoperation unit, the main portal generation and the error extraction unit are connected with the clock unit, the rough measuring unit, the first simulation interpolation unit and the second simulationinterpolation unit, the first simulation interpolation unit is connected with the first figure interpolation unit, the second simulation interpolation unit is connected with the second figure interpolation unit, the rough measuring unit, the first figure interpolation unit and the second figure interpolation unit are connected with the operation unit, and the clock unit is further respectively connected with the rough measuring unit, the first figure interpolation unit and the second figure interpolation unit. The system and method adopt the cascade structure of the simulation interpolation and the figure interpolation to exert technical advantages of two interpolations, and accordingly the time interval measurement distinguishability can be greatly improved.