Abstract: TC4 titanium alloy welded by electron beam was chosens as the specimen to research. The elastic constants of welding seam, heat affected zone and base metal were calibrated through X-ray diffractometer and four-point bending machine, to discuss the difference of elastic constant among these areas. The results show that the testing data of elastic constant of heat affected zone and welding seam were relatively dispersive because of the coarse microstructure. The testing data of elastic constant of base metal were relatively consonant. The calibrated value of elastic constant of TC4 titanium was 12.827×10-6 MPa-1 when tested on diffracted crystallographic plane (213).