Abstract: Four conceptions are proposed of "rigid enterprise", "flexible enterprise", "critical ruin probability" and "maximum tolerable loss". Moreover, based on the four conceptions, a new method is obtained for solving the ruin probability. Meanwhile, the reasons of bankruptcy are found out via mathematical ways. Some other results are achieved, for instance, the certain bankruptcy of enterprises in a finite time, the critical ruin probability of the enterprise and so on.

Key words: rigid enterprise, flexible enterprise, critical ruin probability, maximum tolerable loss