Two experiments were conducted to investigate the effect of probiotics on the malodor removal. In experiment 1, dietary effects (several malodorous gas concentration of excreta, dry matter metabolizability, and blood profiles) were determined using laying hens. A total of 30 Hy-line brown layers, 68-wk of age, were randomly allocated into 5 groups with 3 replicates of 2 birds each. The treatments were probiotics free, 0.2% and 0.4 % addition of mixed probiotics (Bacillus subtilis PNG-4 +Lactobacillus acidophilus LAS), and 0.2 and 0.4 % addition of single probiotics (Bacillus subtilis PNG-4). In experiment 2, the effects of mixing of probiotics into the excreta on the malodorous gas removal was investigated. There were three treatments (probiotics free, Bacillus subtilis PNG-4 +Lactobacillus acidophilus LAS, and Bacillus subtilis PNG-4) with three replicates. The malodorous gas concentrations were detected at 0, 3, 7 and 14 day of incubation. In experiment 1, ammonia concentration was significantly decreased by feeding mixed probiotics at 14th day of incubation. However, amines, hydrogen sulfide, ethylmercapthan, and methylmercapthan were not significantly affected by mixed probiotics. Dry matter metabolizability was significantly increased by feeding probiotics, but no significant differences between single and mixed probiotics. There was no significant differences in blood profiles. In experiment 2, mixing of probiotics into the excreta did not affect the concentration of ammonia, amines, hydrogen sulfide, ethylmercapthan, and methylmercapthan. Therefore, these experiments suggested that Bacillus subtilis PNG-4 + Lactobacillus acidophilus LAS supplementations could improve ammonia gas removal, and dry matter metabolizability in layers. Also, decrease of ammonia concentration was higher in mixed probiotics group compare to the single probiotics group. On the other hand, mixing of probiotics into the excreta appeared not to be a useful method.