To study quantitative change of cerebral blood flow (CBF) on patients with early syphilis, we have established a method on absolute measurement of rCBF by using SPECT with Ethyl Cysteinate Dimmer (ECD) as imaging agent, and the method was applied to measure rCBF on patients with early syphilis. The rCBF values measured by this method are highly consistent with the values measured by other classical methods such as SPECT (123I-IMP) and PET (15O-H2O). The rCBF values for early syphilis patients and the normal control show some statistical differences.A routine quantitative absolute measurement of rCBF featured with simple procedures is therefore on the way of maturation.