Subsurface irrigation has been realized by burying pots, pitchers and subsurface porous pipe, but the present preparation process of porous ceramics could not meet the performance requirements of subsurface irrigation emitters. A new preparation process of clay-based porous ceramics used for subsurface irrigation with minimal cost was explored. The effects of the preparation process (shirking temperature, contents and particle size of slag in the green body) on flexural strength, linear shrinkage and open porosity of porous ceramic were discussed. Finally, the optimal preparation process of porous ceramic with high flexural strength, low linear shrinkage and elevated open porosity were selected. The results showed that the sintering temperature and the contents and particle size of slag in the green body were three key factors influencing the properties of porous ceramics. When sintering temperature was 1075℃ along with content of slag in the green body between 10% and 30%, the porous ceramics showed the best performance with maximum particle size of 0.613mm. Flexural strength of porous ceramic was 9.0~11.0MPa with open porosity of 36.8%~44.8% and the linear shrinkage was 3.8%~4.7%. Therefore, the clay-based porous ceramic could be the appropriate material for subsurface irrigation emitter.