A steering mechanism of an all-terrain vehicle, comprising: a steering shaft; a power steering system; and a connecting portion comprising a first shaft sleeve, a second shaft sleeve, and an elastic membrane assembly, wherein the elastic membrane assembly comprises at least one elastic membrane; the first shaft sleeve and the second shaft sleeve are arranged on two sides of the elastic membrane assembly and fastened to the elastic membrane assembly; an end of the first shaft sleeve away from the elastic membrane assembly is coupled to the steering shaft, and an end of the second shaft sleeve away from the elastic membrane assembly is coupled to the power steering system, wherein the power steering system is splined to the second shaft sleeve. wherein the power steering system comprises a connecting shaft having an external spline, the second shaft sleeve is provided with a shaft hole having an internal spline, and the internal spline is arranged on an inner wall of the shaft hole; and the second shaft sleeve is fitted over the connecting shaft, and the external spline is fitted with the internal spline, wherein the second shaft sleeve comprises a second body having the shaft hole, and a mounting portion arranged on an outer wall of the second body; characterized in that the mounting portion comprises a first mounting block and a second mounting block arranged oppositely, and a gap in communication with the shaft hole is formed between the first mounting block and the second mounting block; and the second body is fitted over the connecting shaft, and the first mounting block is fastened to the second mounting block. a steering shaft; a power steering system; and a connecting portion comprising a first shaft sleeve, a second shaft sleeve, and an elastic membrane assembly, wherein the elastic membrane assembly comprises at least one elastic membrane; the first shaft sleeve and the second shaft sleeve are arranged on two sides of the elastic membrane assembly and fastened to the elastic membrane assembly; an end of the first shaft sleeve away from the elastic membrane assembly is coupled to the steering shaft, and an end of the second shaft sleeve away from the elastic membrane assembly is coupled to the power steering system, wherein the power steering system is splined to the second shaft sleeve. wherein the power steering system comprises a connecting shaft having an external spline, the second shaft sleeve is provided with a shaft hole having an internal spline, and the internal spline is arranged on an inner wall of the shaft hole; and the second shaft sleeve is fitted over the connecting shaft, and the external spline is fitted with the internal spline, wherein the second shaft sleeve comprises a second body having the shaft hole, and a mounting portion arranged on an outer wall of the second body; characterized in that the mounting portion comprises a first mounting block and a second mounting block arranged oppositely, and a gap in communication with the shaft hole is formed between the first mounting block and the second mounting block; and the second body is fitted over the connecting shaft, and the first mounting block is fastened to the second mounting block.