The main laws that govern gentle bunching of Space Charge-Dominated (SCD) beam are considered. It is shown that SCD-beam bunching depends on two main parameters: the first one determines the bunching quality, another one is measure for bunching process duration. The changes in bunching process depending on this parameters and on low of RF-field amplitude increase are described. The optimal conditions of SCD-beam bunching are discussed. The computer codes ZHALO generated for bunching beam characteristic visual representation are described.