We present here a method to complement the number of process parameters at the Parametric Test (PT) of Flash memory. This method focuses on the reconstruction of Flash memory geometry parameters not directly available during Parametric Test (PT). This method is based on the use of a mathematical model generated with a "Design Of Simulation" (DOS) technique. The DOS uses Flash cell simulations results (for different geometries) and outputs, a polynomial equation of the threshold voltages. The parametric test improvement is realized in building complementary geometric distribution from the available measured parameters of the Flash Test Element Groups located in the scribe lines. The geometric distributions are obtained from the mathematical model and do not need complementary measurements. Moreover the calculation is done off-line and does not require extra test time. With this method, widths and lengths distributions of the Flash memory cells are available after Parametric Test (PT).