In order to control and eliminate the harm caused by foreign bodies in luncheon sausages， a method of foreign bodies detection by ultrasonic imaging technology was proposed， and foreign bodies were detected and identified nondestructively. Ultrasonic property parameters， such as ultrasound velocity， acoustic impedance and attenuation coefficient of luncheon sausages and reflection images of different size foreign bodies buried in different depth were obtained by ultrasonic imaging system. And then， foreign bodies were detected and identified according to the reflected signal and ultrasound images. The research showed that inner acoustic images of luncheon sausage with and without foreign bodies had significant differences， the luncheon sausages contained foreign bodies generated a additional echo peak compared with controls. The ultrasound image of luncheon sausages with foreign bodies and controls had significant difference， and the detection rate of foreign bodies form 20 inner acoustic images of luncheon sausage could reach at 96.29% with a threshold of 5 mV of ultrasonic intensity. The best predictive precision of LS-SVM model based on selected characteristic variable can be reached when principal component signals were six， and precision rates of calibration set and prediction set were 93.27% and 81.67%， respectively. The result indicate that ultrasonic detecting system is a feasible way to discriminate foreign bodies in luncheon sausage quantitatively， and has a wide application prospect.