28 adult Min sows (3-7 parities), represented 9 sire families were selected to conduct the continual blood collection from the tail for two hours at the interval of ten minutes between 9:00-11:00 in the morning on the sixth day after the last mating. The content of progesterone was assayed by radio-immunological assay. The amplitudes of the secretion of progesterone were generated by the procedure of HORM fft. exe complied by the author. It is difficult to get a reasonable conclusion from the content analysis, because the content varied widely between different points of blood collection in single sow. After Fourier conversion, the heritability of amplitude for the fifth partial wave was high (h2 = 0.932); middle for the basal, 2nd and 3rd partial waves; lower for others. This supported the idea that prolific sows had more active secretion of progesterone in luteal cells. The coexist of low and high heritability components in amplitude of progesterone secretion showed that the activities of progesterone secretion were influenced by both the genetics and environments. The genetic correlation of basal, 1st, 5th partial waves were negative, the others were positive, with the litter size and litter size alive. It showed that the reproductive performance of Min pigs were not expressed perfectly, as the balance of secretion of progesterone did not reach the best. The genetic correlation of all partial waves with duration of estrus was negative which supported that the progesterone suppresses the estrus. The genetic correlation of 3rd, 5th partial waves were stronger than others, but selection for 5th partial wave would make high responses than the 3rd wave, because the genetic correlation of 3rd partial wave with litter size and litter size alive was positive, therefore, the more appropriats method of selection for progesterone was adopted, the better results would be achieved in the improvement of indirect selection response for litter size.