It was introduced in this paper that a multi-mode control algorithm of PI-Single Neuron based on fuzzy decoupling, this control algorithm can be easily implemented by microcontroller in control systems of temperature and humidity. Under such control system, temperature and humidity are influenced each other. In order to remove the coupling, a new decoupling method is presented, which is called fuzzy decoupling. The static decoupling control is proven very effective when the system is in a static state. But it is not suitable to time-variant systems. In order to reduce the effect in a dynamic state, based on the static decoupling method, a loop is added to modify the decoupling coefficients. The fuzzy controller input is the control object's error of the influenced loop, while the system outputs are the decoupling parameters. The corrected parameters are constantly operated in the decoupling algorithm and the temperature and humidity control system are divided into two relative independent loop systems. Through fuzzy decoupling mentioned, we can use a multi-mode control algorithm of PI-Single Neuron for single loop of temperature and humidity. The PI-Single Neuron control algorithm is composed of PI algorithm and single Neuron algorithm. Different algorithm is chosen according to the absolute of error. The paper gives the structure of single neuron controller and it's simulation results. The paper also provides the simulated output response curves with no decoupling control, static decoupling control and fuzzy decoupling control. As the control algorithm which combines PI control with the single neuron control has strong robustness, good adaptability, excellent anti-interference ability, it is apt to real time control.