Fingerprint sensor (FPS) becomes rapidly popular due to small size and high safety. The molding thickness of capacitive FPS will affect its performance and needs to be accurately measured and controlled. Different from cutting and laser drilling method, one none destructive method with Terahertz electromagnetic wave is introduced. Terahertz wave can penetrate into the molding package materials. The molding thickness can be measured through time delay of two pulse Terahertz waves. The measured thickness is correlated with microscope view and the result is within ±4um gap.