Abstract: A review of ten-year practice developing the ISPRM is given in the hope that some ereative ideas can be drawn from it. The ISPRM stands for the improved simultaneous physical retrieval method (SPRM).The improvement upon the SPRM is associated with the under-determinedness of this ill-posed inverse problem. In the experiment, the precondition is observed that a priori information must be independent of the satellite measurements. The well-posed retrieval theory has told us that the forward process is foundation of the inversion, and it is the bridge between the input of satellite radiance and the output of retrievals. In order to obtain a better result from the forward process, one must take full advantage of every priori information available. It is necessary to turn the ill-posed inverse problem into the well-posed one, and then apply the Ridge regression or Bayes algorithm to find the optimum combination of the first guess, the theoretical analogue information and the satellite observations. so that the impact of the under-determinedness of this inverse problem to the numerical solution is minimized.