A human body tumbling detection method and device and a mobile terminal system are disclosed. The method may include: when detecting that resultant acceleration of a human body is less than a low acceleration threshold a0, capturing a resultant acceleration sequence I0 within fixed time in a two-dimensional coordinate system using resultant acceleration and time as coordinate axes and a0 as a reference line, calculating a curve area above the reference line and a curve area below the reference line that are enclosed by curves in I0 coordinates and the reference line and when a difference between the curve area above the reference line and the curve area below the reference line is less than a curve area threshold ΔS, and time occupied by resultant acceleration below the reference line is greater than a low acceleration time threshold ΔT, determining that the human body tumbles.
