A total of 96 growing pigs (25.11 ± 0.69 kg) were used in this 14 wk feeding trial to evaluate the correlation between crude protein (CP) levels and different space allowances under sawdust bed feeding system on performance in growing–finishing pigs. Pigs were blocked with the following factors: (i) standard space (SS) allowance or wide space (WS) allowance and (ii) basal diet [control (CON)] or 10% reduction in CP of basal diet. The average daily feed intake was significantly increased (P < 0.05) in pigs fed with the CON in the SS. Pigs fed the 10% reduced CP diet in SS significantly increased (P < 0.05) the apparent total tract digestibility of nitrogen and dry matter. The blood urea nitrogen and cortisol concentrations of blood were significantly decreased (P < 0.05) in pigs fed with the 10% reduced CP diet in the SS. The ammonia emissions were significantly decreased (P < 0.05) in the pigs fed the 10% reduced CP diets. The fecal Lactobacillus concentration increased in pigs fed the 10% reduced CP diets in WS. In conclusion, the pigs fed with the 10% reduced CP diet in the SS reduced production cost and odour emissions, improved nutrient digestibility, fecal microbiota, and blood profile in growing–finishing pigs.