This paper uses fractional differential equations to evaluate the mental health of college students. The author first proposes different emotional possibility spaces, such as emotional energy, emotional intensity, and emotional entropy. Secondly, this paper uses Markov chains, fractional differential equations, and other methods to construct emotional models. Its function is a description of psychological characteristics and psychological conditions. Finally, numerical simulations are used to apply the proposed model. This model can well reflect the autonomous transmission of human emotions. This model can provide a new method for establishing the mathematical model of the mental intelligence evaluation system and the mental decision-making system.