The problem of joint designing the base station (BS) precoder, the relay precoder and user equalizers for TDD MIMO amplifying-and-forwarding relay downlink systems is considered. In practical applications, the channel estimation error and the channel reciprocity delay can result in a serious performance loss of a joint designing based on ideal Channel State Information (CSI). Evolved from the distribution of estimation error and the temporal correlation of reciprocity delay, a joint “estimation error-reciprocity delay” channel model that takes both effects into account was established. Based on this model, a channel SVD-based precoding scheme at BS aiming at the first hop transmission was presented, which avoids the feedback overhead of the second hop CSI. Then a joint optimization problem of the relay precoder and user equalizers, which is based on minimizing the sum mean square error (SMSE) of all users with a constraint on the relay total transmit power, was set up. By using KKT (Karush-Kuhn-Tucker) conditions, a closed-form solution to this problem was achieved. Numerical results verify the robustness and effectiveness of the proposed scheme. 