We propose a novel ultra high-definition video coding method with bit-depth reduction before encoding procedure and bit-depth reconstruction after decoding procedure. The bit-depth reduction is performed by Lloyd-Max quantization; considering ultra high-definition video noise reduction for high coding efficiency and gradation conservation for pseudo-contour prevention. The bit-depth reconstruction is carried out accurately using side information which is determined by comparing a local-decoded bit-depth reconstructed image and an original image on encoder side. Experiments show that the proposed method has a pseudo-contour prevention effect and a better PSNR in comparison with conventional video coding methods.