Abstract: In order to ensure the quality of monofilament production，a measurement method of monofilament orientation based on cross-correlation algorithm is proposed，which uses sound velocity method to measure monofilament orientation． STM32 is selected as the microprocessor，the excitation pulse amplification circuit and the receiving signal processing circuit are designed． The single pulse generated by the microprocessor is transmitted to the piezoelectric ceramic sensor at the transmitter through the excitation pulse amplification circuit to generate vibration． The receiving signal processing circuit filters and amplifies the signal waveform at the receiver and sends it to the microprocessor for AD ( Analog-to-Digital) acquisition and storage． According to the principle of correlation，the receiving time difference of the sensor at different positions and the moving distance of the sensor are calculated． The sound velocity of the sound signal in the single wire can be calculated． The orientation degree can be calculated by formula． The experiment shows that the measurement precision of this method is better than 1%．

Key words: degree of orientation, cross-correlation algorithm, STM32 microprocessor