On the basis of range-gated technology, the temporal relation between laser pulse propagation and gated reception was analyzed, and an integrated underwater range-gated temporal model was proposed. The model was validated via specially designed experiments which were carried out on a home-built underwater laser range-gated platform. The good agreements between the experiments and simulations confirm that the model can predict the variations of image contrasts versus delay time, and can be applied to the performance prediction and optimal design of real systems. Furthermore, the effects of the various parameters on the image contrasts versus delay time were discussed, and the measurement of pulse temporal stretching based directly on range-gated technology was also introduced.