Ultrasonic experiments have been performed to measure compressional and shear wave velocities of polycrystalline aluminum under hydrostatic pressure up to 4.1 GPa at room temperature in a multi-anvil apparatus. The sample pressure was determined by the new Z-cut quartz calibrant. Two types of data processing methods, three-order finite strain method and the Anderson?s method, were utilized to calculate the elasticity of aluminum. The results from this work are in good agreement with previously reports and so it demonstrates the accuracy and convenience of our experimental methods, including the validity of the Z-cut quartz calibrant for pressure determination. We believe it?s valuable for the measurements of elasticity of other material in multianvil apparatus, especially those experiments using compressible specimens which have small elastic moduli, and lacking of X-ray source.