The concentration of solid matter in two-phase flow of liquid-solid gradually changes with the variety of height. In order to display this kind of change, professor Nijinren and other people gave an unified formula of concentration distribution. Though the formula is very useful, no one gives it's analytical solution. By using mathematical methods like variable exchanging, variable decomposing, etc, the equation is solved and the analytic solution is first acquired, then the n value of parameter is obtained through the usage of numerical method and experiment data, then the influence of the main factors on n value can be initialy concluded.