Is the reaction with negative Gibbs free energy exothermic?

Not necessarily. There are three important functions in thermochemistry, g, h and s, among which the physical meaning of Δ h (enthalpy) is more complicated, while other physical meanings are more clear. However, under certain conditions, it is not too wrong to vaguely understand the physical meaning of δ H as the change of the heat content of the reaction (such as in high school). S (entropy) is the degree of chaos of the system, and G (Gibbs free energy) you mentioned is the ability of the system to do external work. Δ g represents the work done by the reaction, including a lot of work, including volume work (there will be volume work when the number of molecules changes), electric work, reaction heat and so on. Negative δG is not necessarily exothermic. For example, if we design an ideal Cu-Zn primary battery, the reaction is spontaneous, and δG is negative, but the ideal battery outputs electric work and does not generate heat. In your book, it is said that the reaction with negative Gibbs free energy is exothermic. I guess this is a high school teaching aid. Under the limited conditions of high school, this sentence is universal, but it is a joke to go to college with your knowledge.