Experiments of subsurface irrigation with porous pipe with different soil water lower limits for irrigation was conducted in greenhouse cultivated with tomato, and the results showed that the optimal soil water lower limit for subsurface irrigation with porous pipe was 25～40 kPa. The soil water lower limit for subsurface irrigation with porous pipe is 25 kPa during seedling stage, 25～40 kPa during flowering and fruit bearing stage, and the corresponding applied water is about 0.93 m³/hm².