The study was conducted on injection of calcium chloride at 0, 200, 300 and 400 mMconcentration levels at 45 minutes and 24 hours post-mortem in ~iLongissimus dorsi~i from eight5 year-old cattle to improve beef tenderness. The 2x4 factorial in CRD was used in thisexperiment. The meat quality was studied in terms of shear force value, calpain system protease,collagen content and sensory evaluation. Other meat qualities in terms of color, pH, conductivityvalue, water holding capacity (WHC) and chemical composition were also investigated. The results of the study indicated the conductivity value of the control group was lessthan those of other groups (p<0.01). The pH value, meat color, the chemical composition had nosignificant difference among group (p>0.05) and WHC of beef injected with calcium chloridesuggested an increased drip loss at 45 minutes (p<0.01) as well as 24 hours post-mortemtreatments (p<0.05) and test of interaction showed calcium chloride levels affected drip loss(p<0.01). Thawing loss at 45 minutes case was higher compared to the control group (p<0.05) butthe 24 hours case was not significantly different (p>0.05). The interaction between concentrationlevels of calcium chloride and injection time was found to affect thawing loss (p<0.01). The cooking loss at 45 minutes and 24 hours post-mortem injection but less in the case of had no significant difference (p>0.05). The test of interaction indicated injection time affected cooking loss (p<0.01) 45 minutes but lower than the effect on 24 hours. The results of shear value showed that the control group had higher maximum force (N) than the injected groups (p<0.01). Energy (J) and extension (mm) as well as muscle collagen content had no significant difference among groups (p>0.05). The interaction between calcium chloride level and injection period on shear force value was highly significantly different (p<0.01). The soluble and insoluble collagen content at 45 minutes and 24 hours injection time had no significant difference (p>0.05). The sensory evaluation in terms of temderness and acceptability scores for meat injected with calcium chloride at 45 minutes were higher than that of the control group (p<0.05) but juiciness and flavor scores were not significantly different (p>0.05). Injection at 24 hours had no significantly different (p>0.05) effect on tenderness, juiciness, flavor and acceptability scores among groups. The interaction between calcium chloride levels and injection time on tenderness was significant difference (p<0.05). But there was no significant difference on the content of calpastatin, m-calpain and ~i(+,m)~i-calpain (p>0.05).