Abstract: In the present study， MS， B5 and W media with unchanged organic elements and varied inorganic salt strength of 100%， 75%， 50%， 25% and 0， were selected as materials. With addition of different volumes of 1 mol·L-1 NaOH solution， the pH value of media before and after autoclaving were determined， and solidification state of media were examined to clarify the quantitative relationship between pH value and the added volume of NaOH solution， as well as effects of salt strength on pH value and solidification state of MS， B5 and W media after autoclaving. It was shown that there was a logarithmic quantitative relationship between the added volumes of NaOH solution and pH value of media after autoclaving. The media pH value decreased as salt strength increased， while the volume of NaOH solution needed for pH adjustment increased as salt strength increased. The hardness of media increased as the added volume of NaOH solution increased.

Key words: medium, salt strength, autoclaving, pH value, solidification state