A fast recognition algorithm based on tri-encoding method for one-dimension barcode was presented. First, the image was threshold by OTSU method and the barcode area was separated from the background. Then by analyzing projection characters of the binary image, tri-encoding including 0-1 encoding, similar running length encoding and strip-space encoding was established step by step. Finally, barcodes were found and verified by using table look-up technique from the code table. The procedure of the recognition can strongly handle several kinds of drawbacks like noise, irregularity, deficiency and contamination. Application results show that the correct recognition rate is higher than 99% and the average recognition time is about 5 ms.