Abstract: in engineering seismic refraction exploration in mountainous areas with strong transverse heterogeneity, an observation system with shots distributed in receivers array is often employed. The velocity profile is then inverted from first-arrival times using ray tomography. However, in the case of a long survey line, the influence of the connecting mode of adjacent arrays on the field workload and inverted profile has not been investigated in detail and clearly. This paper examines three observation systems: adjacent arrays connected head to tail, adjacent arrays connected head to tail and with out-array shots, and adjacent arrays with partial overlap. Through an analysis of the ray coverage in a vertical gradient velocity model, the ray tracing and inversion on the two-layer model, and the inversion of the field data, the inversion quality and field workload of the three observation systems are evaluated comprehensively. Because of its best inversion effect and the lowest field burden, the system with adjacent arrays connected head to tail and with out-array shots is considered to be optimal observation system.