Provided are a three-dimensional space coordinate detection method, a three-dimensional input method and corresponding devices. The detection method includes the steps that the three or more sets of ultrasonic ranging devices arranged on the periphery of a mobile terminal but not on the same straight line are used for measuring near-point distances and far-point distances of a quasi finger target, the obtained three or more sets of near-point distances and far-point distances are used and combined with space coordinates of the corresponding ultrasonic ranging devices, and calculation central point coordinates of the quasi finger target are obtained through calculation. The three-dimensional input method includes the steps that when it is detected that a preset trigger action is triggered, the ultrasonic ranging devices arranged on the periphery of the mobile terminal but not on the same straight line are started to trace and measure the three-dimensional space coordinates of the quasi finger target, and the three-dimensional space coordinates are correspondingly displayed to the mobile terminal. Users can finish the input operation without using an extra remote control or a writing pen or a finger stall or other extra assistant electronic devices, and operation is free, convenient and rapid.