The present invention is related to a direct solid sample analytical technology for determining a content and a uniformity thereof in a lyophilized kit of a sulfur-containing chelator with a stable complex capacity for radiotechnetium (Tc-99m) and radiorhenium (Re-186, Re-188). An economical, stable and easily accessible coal standard is used herein as a contrast substance to construct a sulfur calibration curve, followed by obtaining the sulfur content and the uniformity thereof in the solid lyophilized sample by interpolating the foregoing result into the sulfur calibration curve. Then, the weight content percent is converted to get the content and the uniformity of the chelator in the lyophilized kit. The quality control of active pharmaceutical ingredients (API) in the lyophilized kit during key production processes and clinical applications is thus assured.