To improve the space comfort of manned submersible compartment, a multi-source composite evaluation method based on virtual simulation technology was proposed to evaluate the space comfort of deep-sea manned submersible compartment under strong constraints. Based on virtual simulation technology, the method combines three-dimensional digital data of manned submersible compartment space with human data of submersible to construct a digital virtual simulation model. By regarding rapid correspondence and evaluation as criterion, human comfort was divided into zones, and the space and function characteristics of manned submersible were systematically analyzed. Through acquiring human comfort zone characteristics and space constraint mapping based on human physiological characteristics, seven evaluation indicators were established. Six human factors assessment tools were combined to build a multi-source composite comfort evaluation model. The visual evaluation system of space comfort was developed by virtual simulation technology, and the feasibility of the multi-source composite evaluation method and the visual evaluation prototype system was validated by optimizing the space design of a manned submersible cabin. The research shows that different task postures seriously affected the accuracy of human comfort assessment. The narrow cabin space and the layout of equipment in cabin further increased the difficulty of job posture assessment. The composite evaluation method of spatial comfort could accurately describe the degree of spatial comfort under various postures. At the same time, the technical characteristics of multi-source and visualization improved the efficiency of evaluation of spatial design schemes and the readability of evaluation results to a certain extent.