Unusual niches are herein defined as ecological systems which cannot support growth and reproduction of most fungi.Only a small number of fungi are able to survive in these unusual niches and develop special cell structures, metabolic pathways and evolution mechanisms for adaption.We divide the unusual niches into three categories: i) the niches with specific physical or chemical limited factors; ii) the niches with special substrates; iii) the unusual niches limited by integrated factors.We studied the fungal diversity from the niches with specific physical or chemical limited factors (such as low temperature) and the niches with special substrates (such as rock and wetland).