In this paper, channel estimation has been studied in MIMO-OFDM systems. Pilot symbols have been widely employed in many applications and standards. In conventional approaches, pilot symbols are multiplexed among data stream, based on an exclusive pattern, on each transmit antenna. Since pilot tones do not carry data information, thereupon, this method results in lower bandwidth efficiency. To cope with this problem, an approach based on combined pilot and data symbols streams had been proposed. In this approach, data symbols interference results in inaccurate channel estimation. However, using iterative estimation algorithms and in cost of high complexity, its improper performance could be compensated. In this paper we introduce a pilot structure which estimates the channel appropriately and at the same time keeps the spectrum efficiency acceptable. Simulation results represent improvement in estimation performance in comparison with other conventional approaches.