The line shapes of AlⅠ(394.4 nm) and Al I(396.1 nm) were theoretically simulated based on the one-dimensional radiative transfer model without self-reverse effect. In order to get a more reliable result, an model improvement of the parameter handling approach was made to minimize the number of independent parameters. The revolution of spatial population density distribution of species was shown in different delay times. The effects of population density distribution parameters to the line profile were studied. The relationship between the depth of self-reverse and the population density distribution parameters ratio of lower and upper levels were analysed. A method to judging the line shift was experimentally verified by studying the effects of shift parameter to line profile too.