Genetic analysis is an important part of undergraduate genetics teaching and tetrad analysis is unique and integral for genetic analysis of fungi. The ordered tetrad in Neurospora is an important material for genetic analysis, which can not only be used to study recombination between genes and centromeres, but also between genes themselves, as well as study the fine cross patterns between non-sister chromatids of homologous chromosomes. However, in textbooks and related professional journals, there is a lack of specific introduction to the induction methods of the seven basic class asci used in two genes analysis. In the present paper, we designed a table presenting the correlation between the three tetrad types (PD, NPD, T) and the four segregation pattern groups (Ⅰ Ⅰ, Ⅱ Ⅱ, Ⅰ Ⅱ, Ⅱ Ⅰ) to visually show the 12 possible combinations (3×4=12). Then five of them were excluded through the "×" symbol and in addition with three comments attached with the table, thus finally we obtained seven basic ascus types. We hope that this analytical method can assist the teaching of ordered tetrad analysis in Neurospora.