This paper deals with discrete-time stochastic singular systems with multiplicative-noise and input delay.A finite-horizon linear quadratic (LQ) optimal control problem is investigated.The stochastic maximum principle is first established for singular systems in discrete case, and then a sufficient unique existing criterion for the optimal control is derived.The method to obtain the main results depends on the relationship between the optimal state and the auxiliary variable, which avoids using the augmented arguments.A numerical example is provided to demonstrate the effectiveness of theoretical results.