A momentum balance equation is developed to investigate the magnetotransport properties in monolayer molybdenum disulphide when a strong perpendicular magnetic field and a weak in-plane electric field are applied simultaneously. At low temperature, in the presence of intravalley impurity scattering, Shubnikov–de Haas oscillation shows up accompanied by a beating pattern arising from large spin splitting and its period may halve due to the high-order oscillating term at large magnetic field for samples with ultrahigh mobility. In the case of intervalley disorders, there exists a magnetic-field range where the magnetoresistivity almost vanishes. For a low-mobility layer, a phase inversion of oscillating peaks is acquired in accordance with recent experiment. At high temperature when Shubnikov–de Haas oscillation is suppressed, the magnetophonon resonances induced by both optical phonons (mainly due to homopolar and Fröhlich modes) and acoustic phonons (mainly due to intravalley transverse and longitudinal acoustic modes) emerge for a suspended system with high mobility. For the single layer on a substrate, another resonance due to surface optical phonons may occur, resulting in a complex behavior of the total magnetoresistance. The beating pattern of magnetophonon resonance due to optical phonons can also be observed. However, for a nonsuspended layer with low mobility, the magnetoresistance oscillation almost disappears and the resistivity increases with field monotonically.