A pitch determination method based on AMDF (Average Magnitude Difference Function) is proposed in this paper. The AMDF is often used to determine the pitch parameter in real-time speech processing applications. Falling trend of AMDF at higher lags, however, makes the method vulnerable to octave errors (pitch doubling or halving). In this paper, we propose an alignment technique that effectively eliminates the falling trend by aligning the AMDF peaks along a straight line. Experimental results on speech signals spoken by male and female speakers show that the current method can reduce the occurrence of octave errors in greater numbers when compared with other AMDF based functions.