With the application demand of optical metrology based on correlated photons method in recent years, spectral distribution of type-I noncollinear spontaneous parametric down-conversion (SPDC) is theoretically analyzed. Two different cases including ideal phasing-matching and nonideal phasing-matching are considered, SPDC spectral distribution curve is formed by 355 nm CW laser pumping type-I noncollinear BBO crystal, and numerical simulation results show that two cases have almost the same spectral distribution. Lastly measurement experiment of SPDC spectral distribution is designed. The experiment shows type-I noncollinear SPDC spectral distribution is in good agreement with numerical simulation.