The invention discloses a computer software automatic installing method, if a computer has been installed with a main operating system, detecting if the appointed software or program is accurately installed into the main operating system according to preset rules: if not, loading an automatic installation software to load the appointed software or program according to the preset rules; loading a main operating system booting program, handing over the control right to the computer system to the main operating system, and completing normal booting of the main operating system. The invention improves safety and reliability of the main operating system and also reduces network system management costs and raises management efficiency.