Abstract: In order to solve the control problem of refrigeration system with time-delay characteristics，an improved model-free adaptive predictive control algorithm is proposed． The improved model-free adaptive predictive algorithm is applied to the refrigeration system control scheme． And in order to get more stable control effects，better performance of the algorithm，and make design of MFAPC ( Model-Free Adaptive Predictive Control) more flexible． Firstly，a parameter estimation control scheme that introduced two parameters L1 and L2 is proposed，It improves the pseudo-partial derivative parameter estimation process of the MFAPC，therefore the algorithm can improve the stability effect while achieving the goal of reducing reference． Then，The control output error sum is added to the control input criterion function． Finally，typical linear and nonlinear time-delay system，tracking time-varying signal system，lithium bromide refrigeration system are introduced． The tracking control problems are simulated and compared． The simulation results show that the improved model-free predictive control algorithm can achieve more stable output result，with faster response speed and better control performance，solving the refrigeration system control problem of time-delay characteristics．

Key words: model-free predictive control, pseudo partial derivative, parameter estimation, error sum, lithium bromide unit