In view of the basic problems and principles of statistics, the elements of direct calculation for design allowable value of metallic material tensile strength at room temperature were briefly analyzed. The design allowable values for TC11 titanium bar and forging were calculated and analyzed. Result showed that the lower limit of series allowable values for TC11 bar with different sizes calculated by regression method was closer to the actual product strength compared with specified S-basis values. The calculated ultimate strengths were 31-85 MPa higher than specified lower limit. The allowable value calculated by non-regression method for TC11 forging ultimate strength was 11 MPa lower than specified S-basis value. Calculated values were higher than A-basis values of TC11 alloy in domestic material data handbooks, ie 15%-72% higher for bars, 39% and 52% higher for forging ultimate strength and yield strength.