We report a mechanism of the continuous pitch variation of the cholestric liquid crystal (CLC) with reactive mesogen based on the phase separation model and the 4 x 4 matrix analysis. From the density variation of the polymerized RM with chirality, the corresponding pitch variation was directly estimated and the reflectance was calculated using the 4 x 4 matrix analysis. The calculated result quantitatively coincided with the experimental result with broadband reflection spectrum. Also, we demonstrated a simple transflective LC display using the CLC white reflector with broadband reflection spectrum covering entire visible range.