It is known that the welding process in the production field must be applied in. a certidn welding sequence. Accordingly, residual stresses as well as deformation can be controlled by temperature distribution on welded plates. In this case the welding length (length of block) nost be suitable in order to control interpass temperature between a weld and other (block and other) on the same we-ld line .Where the interpass temperature has a great influence with heat input. This paper presents a new technique for the estimation of optimum welding length as a function of heat input. This method depends on the calculation of cooling rates as a function of heat input. Then the time required for cooling to a certain temperature can be determined. The calculations are transferred into figures from which any date such as cooling rate and welding time can be obtained. The deduced time will be the total welding time till certain cooling time. The optimum welding length can be estimated on the basis of the electrode specifications such as size, kg weld metal per kg electrode, number of electrodes per kg weld metal, burn off time per electrode and welded length per burn off time per electrode. The possibility of application of such technique in shipbuilding is investigated. It is concluded thatthe proposed technique for estimating of optimum welding length can be applied effectively for controlling the residual stresses and deformation due to welding.