Aeromonas caviae can secrete several chintinases with different molecular weights. One chitinase gene chi 1 has been cloned and sequenced. It encodes a protein of 865 amino acids with a signal peptide at the N-terminus, a polycystic kidney disease(PKD)-like domain, a triosephosphate isomerase(TIM) catalytic region, a receptor for egg jelly(REJ)-like domain and two tandem chitin binding domains (ChBDs). The entire chitinase degrades colloid chitin both endolytically and exolytically into N-acetylglucosamine, chitobiose and chitotriose. When removing the 302 amino acids at C-teminus its activity remains but the degraded products are chitobiose, chitotriose and chitotetraose. The study shows that for the full-length chitinase, its substrate with the shortest length is chitotriose while in its truncated form, it is chitotetraose.