A nonlinear function operation device and method are provided. The device may include a table looking-up module and a linear fitting module. The table looking-up module may be configured to acquire a first address of a slope value k and a second address of an intercept value b based on a floating-point number. The linear fitting module may be configured to obtain a linear function expressed as y=k×x+b based on the slope value k and the intercept value b, and substitute the floating-point number into the linear function to calculate a function value of the linear function, wherein the calculated function value is determined as the function value of a nonlinear function corresponding to the floating-point number.