To study the representative dose coefficients near nuclear facilities in the arid regions of Northwest China, a simplified anatomical model of Sphingonotus insects using computed tomography (CT) scanning is proposed. In addition, a voxel model created by using Photoshop and Python is used to assess the results of the simplified anatomical model. The dose coefficients of internal and external ⁹⁰Sr and ¹³⁷Cs irradiation on different organs of Sphingonotus insects in the environmental medium are calculated. To verify the feasibility of the proposed model, the results are compared with the dose coefficients reported in the International Commission on Radiological Protection (ICRP)Publication 108. Based on the simplified model adopted by ICRP to arrive at the results reported in Publication 108, the average value of dose coefficients of each organ of the insect is used to calculate the results presented in this paper. The dose coefficients of internal and external ⁹⁰Sr irradiation for the simplified anatomical model of Sphingonotus were found to be 6.59×10^-4 μGyh^-1/Bqkg^-1 and 6.74×10^-4 μGyh^-1/Bqkg^-1, respectively. Meanwhile, the dose coefficients of internal and external ¹³⁷Cs irradiation for the simplified anatomical model were 1.34×10^-4 μGyh^-1/Bqkg^-1 and 4.40×10^-3 μGyh^-1/Bqkg^-1, respectively. The dose coefficients were 7.87×10^-4μGyh^-1/Bqkg^-1 and 6.74×10^-4μGyh^-1/Bqkg^-1, respectively. The dose coefficients were 1.33×10^-4μGyh^-1/Bqkg^-1 and 3.51×10^-3μGyh^-1/Bqkg^-1, respectively. The dose coefficients of internal and external ⁹⁰Sr radiation for reference insects as reported in the ICRP Publication 108 were 1.00×10^-2 μGyh^-1/Bqkg^-1 and 3.90×10^-10 μGyh^-1/Bqkg^-1, respectively. Moreover, the dose coefficients of internal and external ¹³⁷Cs radiation in the ICRP Publication 108 were 3.20×10^-3 μGyh^-1/Bqkg^-1 and 2.80×10^-3 μGyh^-1/Bqkg^-1, respectively. The above data indicate that the dose coefficients of internal irradiation reported in the ICRP Publication 108 are larger than those calculated using the proposed dosiological model, whereas those of external irradiation in ICRP Publication 108 are smaller. This trend is probably related to the size of the organism, decay rate, and energy of radionuclides. The adoption of a simplified anatomical model, morphologically similar to the organism, and a voxel model, highly overlapping with the organism, in this study allows a visualization of the real exposure situation for the organism considered with high accuracy, proving the feasibility of the insect dosimetry model established in this study.