A Modified Simulated Annealing Algorithm (MSAA) is proposed as a statistical technique for obtaining approximate solutions to combinatorial optimization problems. The Proposed algorithm is a combination of Simulated Annealing (SA) and Hamming Scan algorithms. It combines the good methodologies of the two algorithms like global minimum converging property of SA algorithm and fast convergence rate of Hamming scan algorithm. Spread spectrum communication systems and Multiple radar systems can fundamentally improve the system performance by using a group of specially designed orthogonal binary/polyphase coded signals. But the synthesis of orthogonal codes with good autocorrelation and cross-correlation properties is a nonlinear multivariable optimization problem, which is usually difficult to tackle. In this paper MSAA is used to synthesize orthogonal coded sequence sets of good correlation properties. Some of the synthesized results presented here have correlation properties better than other known in the literature. The convergence rate of the algorithm is also good.