This study was performed to know the effect of depolymerized alginate obtained by hydrolysis of alginate through a heating process at $121^{circ}C$ on intestinal environment, Rats were fed with diets containing $1\%$, $5\%$, and $10\%$ of each depolymerized alginate (HAG-10, HAG-50, HAG-100 and alginate) for 35 days, The changes of weight, moisture content, pH and volatile basic nitrogen (VBN) of fecal, and a short chain fatty acids (SCFA) were checked in the rats. The fecal weight and moisture content were the highest in rats fed with alginate diets (p<0.01), followed by HAG-100, HAG-50 and HAG-10 in order. The $5\%$ of HAG-50 diets induced a significant increase in contents of protein and lipid of feces, resulting in the decrease of apparent digestibility of protein and lipid (p<0.01). The pH and VBN content in feces of the rats decreased in $5\%$ and $10\%$ of HAG-50 diets, but $10\%$ of HAG-100 diets; $5\%$ and $10\%$ of alginate diets brought about an increase of fecal pH and VBN (p<0.01), The amount of n-butyric acid in feces was increased while propionic and acetic acid contents decreased significantly (p<0.01) in diets containing $5\%$ and $10\%$ HAG-50. However, the feces of rat fed diet containing $5\%$ and $10\%$ alginate showed a tendency to being opposite in results than that of HAG-50.