The invention discloses a method for identifying the 
protoplast monokaryon mating types of 
lepista sordida and a special primer pair SR-4*2 thereof. The method comprises the following steps of: with 
genome DNAs (deoxyribonucleic acids) of the 
protoplast monokaryons of two plants of 
lepista sordida to be identified as templates, performing PCR (
Polymerase Chain Reaction) amplification by using a PCR primer pair composed of two 
single chain DNAs as shown in SEQ ID No.1 and SEQ ID No.2, and detecting the sizes of the obtained PCR products; if the PCR products of the 
protoplast monokaryons of the two plants of 
lepista sordida to be identified both contain or do not obtain 500 bp-800 bp of 
DNA segments, indicating that the 
mating types of the protoplast monokaryons of the two plants of lepista sordida are the same; and if one 
plant contains 500 bp-800 bp of 
DNA segments, while the other 
plant contains no 500 bp-800 bp of 
DNA segments, indicating that the 
mating types of the protoplast monokaryons of the two plants of lepista sordida are different.