This article investigates the bipartite consensus problem for a class of multi-agent systems (MASs) with parameter uncertainty and leader of nonzero input under a signed digraph. Due to the unknown and time-varying input signal of the leader, followers are unable to obtain accurate information about the leader. For this purpose, a distributed adaptive observer is designed based on parameterization theory. Then, considering the existence of parameter uncertainty in the MASs, an auxiliary function is designed to compensate the impact of uncertainty. Afterwards, an adaptive controller with dynamic coupling gain is designed based on observation errors and auxiliary function. Subsequently, it is demonstrated that the MASs with parameter uncertainty and leader of nonzero input can achieve bipartite consensus by stability analysis. Finally, the effectiveness of the proposed scheme is verified through simulation.