The digestive system and immune system of newly ablactated piglets are ateliotic, thus can not secre The digestive system and immune system of newly ablactated piglets are ateliotic, thus can not secret enough gastric acid to retain the gastroenteric pH value in an appropriate level. When the acidizer is added, the gastroenteric acidity will increase so as to restrain the reproduction of the detrimental bacteria and promote the reproduction of beneficial bacteria in rear end of the intestines. In this way the microbial system in enteron and the piglets' disease resistance will be improved so that some diseases especially diarrhoea will be largely restrained. Meanwhile, an acidic environment can activate pepsin and digestive enzyme, therefore can help piglets grow healthily.