This paper presents the joint semiblind equalization and decoding algorithms based on linear programming (LP) in the low density parity check coded multiple input multiple output orthogonal frequency division multiplexing systems with different modulation methods, in which the signals are affected by multiple antenna interferences, multipath fading and additive noise. When a nonaffine quadrature amplitude modulation is utilized, some new constraints are developed, which guarantees the correctness of joint decoding. Furthermore, pilot symbols are applied to estimate the channel state information needed in Turbo receiver and joint detection and decoding based on LP. Simulation results indicate that when only a small number of pilots are available, the existing detection techniques based on channel estimation exhibit error floors. In contrast, the proposed receiver performs well in the whole simulated regions.