This study was conducted to investigate the effects of dietary complex probiotic preparation (CPP) and innulin (IN) on growth performance, nutrient digestion, rumen fermentation and blood metabolism of fin⁃ ishing bulls. A 2×2 two⁃factor completely randomized design was adopted, and the principal factors were CPP (dietary no added or added 20 g / d CPP) and IN (dietary no added or added 2% IN), respectively. Twenty 1⁃year⁃old healthy Simmental crossbred bulls with body weight of (403±12) kg were randomly divided into 4 groups with 5 bulls per group. Bulls in the four groups were fed with basal diet, basal diet+CPP, basal diet+IN and basal diet+CPP+IN, respectively. The pre⁃experimental period lasted for 10 days, and the experimental pe⁃ riod lasted for 60 days. The results showed as follows: 1) dietary CPP or IN significantly increased the final weight and average daily gain of finishing bulls (P<0.05), and significantly decreased the feed to gain ratio (P<0.05) . The CPP and IN interaction significantly increased the average daily gain of finishing bulls (P < 0.05) . 2) Dietary CPP significantly increased the apparent digestibilities of dry matter, crude protein and neu⁃ tral detergent fiber (P<0.05) . Dietary IN significantly increased the crude protein apparent digestibility (P < 0.05) . The CPP and IN interaction trended to increase the crude protein apparent digestibility (P = 0.063) . 3) Dietary CPP significantly increased the concentrations of propionate and ammonia nitrogen in rumen (P < 0.05), significantly increased the numbers of Ruminobacter albus, Fibrobacter succinogenes, Butyrivibrio fibrisolvens and Prevotella ruminicola (P<0.05), and significantly decreased the protozoa number (P<0.05) . Dietary IN significantly increased the rumen pH (P<0.05), and significantly increased the propionate concen⁃ tration and Fibrobacter succinogenes and Butyrivibrio fibrisolvens numbers in rumen (P<0.05) . The CPP and IN interaction trended to increase the rumen Butyrivibrio fibrisolvens number (P = 0.069) . 4) Dietary CPP sig⁃ nificantly increased the total antioxidant capacity and contents of glucose and total protein in serum (P<0.05), and significantly decreased the contents of urea nitrogen and malondialdehyde in serum (P<0.05) . Dietary IN significantly increased the contents of glucose and total protein in serum (P<0.05), and significantly decreased the serum urea nitrogen content (P<0.05) . The CPP and IN interaction trended to increase the serum total pro⁃ tein content (P = 0.089) . In general, dietary CPP or IN alone can increase the Fibrobacter succinogenes and Butyrivibrio fibrisolvens numbers and propionate concentration in rumen, improve the crude protein apparent di⁃ gestibility and nitrogen utilization, thereby improve the growth performance and feed efficiency of finishing bulls. The CPP and IN interaction trend to increase the Butyrivibrio fibrisolvens number, crude protein apparent digestibility and protein synthesis, thus improve the growth performance of fattening bulls.