通过跟踪光束在积分球内的多次反射过程，建立了积分球出口辐出度与积分球结构参数的关系。依据积分球内置光源的能量转换关系，建立了积分球开口处光谱辐出度与内置光源参数及积分球自身结构参数之间的理论关系模型。此外，选用具体的积分球内置光源参数，利用建立的模型计算出积分球开口处光谱辐出度理论值，并用标定好的光谱仪对该模型进行了实验测量与不确定度分析。结果表明：在0.6m～0.85m波段范围内，该模型计算值与实验测量值相对误差均小于4%；由于光谱仪自身响应特性及标定光谱仪的黑体温度的影响，0.9m处相对误差为8.65%。

According to the requirements for the absolute calibration of spectrometer, a diffusing source formed by integration sphere was analyzed. The theoretical model of the spectral irradiance at the exit of an integration sphere was established and analyzed with a spectrometer. The calculation and experiment results confirmed the validity of the model. In the band of 0.6m～0.85m, the calculated value obtained from the model has an error of less than 4% compared to the measured value; at the wavelength of 0.9m, the error is 8.65% due to response property of the spectrometer itself and the blackbody for calibrating the spectrometer. It is showed that the model can be used to calculate the radiation value of integration sphere source.