As a single photon state, the correlated photon is often applied to quantum communication and optics metrology domain. The study of the spectral radiation and intensity distribution of the photon has a great significance for the broad-band radiometric calibration. The space distribution of the correlated photon spectra circle generated by type-I Spontaneous Parametric Down Conversion(SPDC) was simulated theoretically. Based on the simulation, the corresponding experimental measurement system was established. In this system, 355 nm laser is set to pump the BBO crystal, the type-I correlated photon spectra circle is detected by a Complementary Metal Oxide Semiconductor (CMOS) camera. The dot-matrix scanning method is used to record the circle. The spectral distribution of the measurements is 430 nm~860 nm. The results show that the spectra circle diameters of experimental results are highly consistent with the theoretical ones, the spectra circle distribution of type-I SPDC is homocentric and the spectra of the correlated photon has a broad band.