The invention provides a liquid crystal aligning agent and a liquid crystal display element. The liquid crystal aligning agent contains silarylene. Perferably, the silarylene comprises a polymer provided with a repetitive unit shown in formula (P). By employing the liquid crystal aligning agent, a liquid crystal aligning film which is high in reliability can be formed, the reduction of the voltage holding ratio of the liquid crystal aligning film for a long time is less, and even under severe service conditions, the liquid crystal aligning film does not generate residual images, and the coating property of the liquid crystal aligning agent is good.