An image frame transmission method for use in a network transmission system is provided. The network transmission system includes an image sensor and an image processor. Firstly, a first image data segment of an image frame captured by the image sensor is outputted to the image processor in response to a first state of a control signal after an initial signal has been asserted by the image processor. Then, the output of a second image data segment of the image frame following the first image data segment to the image processor is delayed in response to the transition of the control signal from the first state to a second state. Afterward, the second image data segment is outputted to the image processor in response to the transition of the control signal from the second state to the first second state.