Unlike video coding, video deinterlacing relies heavily on the correctness of motion. To obtain more reliable motion, we propose a new motion search criterion that imposes constraints on the motion diversity among neighboring blocks, and improve the symmetric ME method by dynamic block splitting and single direction ME. To further improve the visual quality, adaptive deinterlacing algorithm based on block variances is also proposed. Extensive experimental results demonstrate that the proposed techniques significantly improved the deinterlaced video quality, both PSNR-wise and visually.