Abstract: In an experiment, several pieces of porous biomass concrete (PBC) were prepared out of sawdust and soaked in clean water separately and use the water separately to soak seeds for germination test. Results show that in terms of compressive strength and porosity, the optimum formular of the PBC was 0.55 in water-cement ratio, 15% cement and 1.0% sawdust or or 0.60 in water-cement ratio, 5% cement and 2.5% sawdust. Once the PBC was put into water, COD, pH and EC of the water rose quickly in a short time and reached 76.4mg•L^-1, 9.93 and 4.4 mS•cm^-1, respectively, on average after 40 days of immersion. Under the same condition, COD content of the PC (ordinary porous concrete) soaking water was 9.9mg•L^-1, or only 13.0% of PBC's. but pH and EC of the water was higher than that of the PBC’s. The immersion test shows that both the PBC and the PC decreased in porosity by 3.2, and 4.8 percentage points, respectively. And the germination test shows that the PBC did not affect much seed germination of vegetables. The findings suggest that the PBC is an effective carbon source to microbes in water and can reduce pH and EC of the water and slow down the process of clogging pores of the concrete.