This essay was written about philosophical despair and investigating the causes and factors of its creation in the poetry of Simin Behbahani. The chosen research method for that, is the "thematic analysis" method; in this order, all the themes were extracted from the poems and the high frequency of philosophical themes and their fusion with philosophical despair caused this article to investigate its causes and factors by referring to Simin's speech. The results of the research show that, the sonnet, in addition to all the content functions has had so far, it can also have the capacity to express philosophical issues, as Simin Behbahani in his sonnet has raised philosophical topics such as creation, death, determinism, time, etc. due to the fact that all these concepts in her sonnet are associated with a kind of philosophical despair and it can be observed sometimes explicitly and indirectly- referring to signs such as pessimism and objection to creation, wish for death, delay and slowness of time, death of belief and belief in Internal and social constraints - in her poems. Part of the causes of this despair can be considered to be rooted in personal issues such as family problems, passing of life and the experience of old age and sensitivity of the poet, loss of friends and loved ones, and part of it is related to the social and political issues of his society that it is full of suffocation and darkness for the poet, it is relevant