The invention relates to a GPU reverse time migration method and system based on multi-flow optimization, relating to the field of geophysical exploration. The method comprises the following steps: acquiring seismic data; performing reverse time imaging processing on the seismic data, and calculating a data loading kernel function, a wavelet back-propagation kernel function and a data back-propagation kernel function during processing by adopting a primary concurrent calculation method; calculating an imaging condition kernel function and a noise filter kernel function in the reverse time imaging process on the seismic data are calculated by adopting a secondary concurrent calculation method; obtaining an imaging result according to the calculation results, and generating an imaging profile. The pre-stack reverse time migration calculation of the seismic data is accelerated by adopting a multi-flow parallel optimization strategy. The method not only can process ultra large-scale seismic data, but also can improve the migration processing efficiency.