In most relatively shallow waters, fixed platforms are the optimum economical choice. One of the important aspects of offshore fixed platform design is their installation procedure. Among the several conditions during installation, launching is probably the most critical. This operation has to be modelled and examined carefully in order to insure safe separation of jacket from barge. Sensitivity studies are performed to clarify the influences of the initial condition of launch barge to the jacket launch process. Launch analysis is carried out by using numerical simulation methods that supported by MOSES software. Jacket structure and launch barge are modelled on SACS and MOSES respectively. The jacket structure is laid on top of barge with the position of the top of jacket in the stern launch barge. Simulation results on the base case with a barge initial trim is 3.5° and a draft at midship is 6.1 m show that the jacket launch process can take place safely. Sensitivity analysis shows that the greater the trim angle and the initial draft of the barge the shorter the sliding speed and the reaction of the rocker arm decreases. While changes in the LCG jacket and the additional weight of the jacket have a significant effect on the bottom clearance and jacket free floating conditions after being separated from the launch barge.