In order to investigate the genetic diversity and estimate the genetic abundance of natural populations of Pleurotus eryngii var. tuoliensis, mating type factors in 84 protoplast monokaryons derived from 51 isolations collected from Xinjiang were analyzed. There were 54 different A factors and 59 different B factors in the 84 monokaryons. Chi-square test indicated that A and B factors were distributed with equal probability. Therefore there would be 79 different A factors and 100 distinct B factors in natural populations of P. eryngii var. tuoliensis in Xinjiang, China, and the putative mating type factors from monokaryon are 7,900, and for dikaryon, there would be 31,201,050 in nature. In conclusion, genetic diversity of P. eryngii var. tuoliensis is very high in Xinjiang, and Xinjiang is a valuable wild P. eryngii var. tuoliensis germplasm resource pool.