The work aims to propose a modified PSO algorithm based on H∞ theory with small search space and objectively initialized particle swarm (HOI-PSO) regarding the problem that during tuning PID controller parameters for large time delay processes, particle swarm optimization (PSO) with large search space will have poor search ability and even cannot converge. H∞ theory was used to determine the initial search band for PSO. Information entropy was integrated to evaluate and tune the initialized particle swarm in order to get the initial population of higher dispersion. Matlab simulation showed that, HOI-PSO algorithm could enhance the convergence speed of PSO algorithm and had the similar or even better global optimization capability as the scope of large range search; for large time delay process control, the control performance of the closed loop system was greatly improved. The results of the application of HOI-PSO algorithm in the control of the basis weight loop of the fourdrinier paper machine show that, the PID controller parameters tuned by the information entropy PSO algorithm have good control effect on the large time delay process and provide certain theoretical guiding significance in actual production.