In this thesis, we propose and evaluate quasi-optimal algorithms for solving the code-constellation optimization problem in M-ary CDMA system. The M-ary CDMA system is a new CDMA architecture. The more spreading codes are used, the higher bandwidth efficiency can be achieved. We use a code, which we refer to as mapping code, to form a multi-dimensional spherical code-constellation. The M codewords of the mapping code correspond one-to-one to the M points on the code-constellation. Thus, the code-constellation optimization problem is a combinatorial optimization problem. Initially, we present a few algorithms to solve the issue, including exhaustive search (ES) and symmetric points search (SPS), where the latter one is able to reduce computation complexity, but still taking quadratic time to solve the problem. Finally, we propose a quasi-optimal algorithm, namely Manhattan distance search (MDS) algorithm. Numerical results and comparisons are provided to illustrate that the computation complexity of the Manhattan distance search algorithm increases linearly with dimension of code-constellation, and its performance is much better than others.