The raw material control, concrete mixing proportions and skilled level of manual operation are the main factors for quality of shield segment manufacturing. The practice shows that the pH value of curing water also has some influence on it. In order to obtain the optimal pH value of segment curing water, segments and test pieces produced at a same time are divided into 6 groups and cured for 7 days in water with pH values of 7, 8, 9, 10, 11 and 12. After 28 days, the colour of the appearance of segments and test pieces are observed; and then the compressive test and antipermeability test are carried out. The results show that: 1) The colour of segment appearance darkened (from gray to dark) and the compressive strength and antipermeability strength of segment decrease as pH value of segment curing water increases. 2) The colour of segment appearance remains original and the compressive strength and antipermeability strength of segment vary little under the pH value of 7-10 of the segment curing water. 3) The colour of segment appearance darkened and the compressive strength and antipermeability strength of segment decrease rapidly under the pH value of segment curing water larger than 10. Thereby, the rational pH value range of segment curing water is 7-10. 