Pitch period is a key parameter in speech compression

synthesis and recognition.The well-known AMDF is often used to determine this parameter.But it is easy to make the estimated pitch doubled.With the problem

this paper analyses the features of the AMDF and its disavantages that occur in pitch detection.And a new function

Circular AMDF(CAMDF)

is proposed.The CAMDF conquers the defect of the AMDF effectively

and simplifies the process of pitch detection.With the properties of CAMDF

a new pitch detection algorithm based on CAMDF is described.The algorithm not only simplifies the pitch detection

but also effciently decreases the estimation errors and improves the precision of estimated values.Lots of experiment show that the performance of the algorithm is better than other methods that are based on the AMDF or the LVAMDF.