The utility model provides a small -size PSA and small -size deep cooling air separation's composite set, it is main includes PSA nitrogen making system and the empty oxygen generation system that divides, the empty oxygen generation system of branch include and divide the connecting pipe to connect the air cooling tower and connect molecular sieve purifier through the air cooling tower through empty, molecular sieve purifier connect out two the tunnel at the back, connect all the way in turboexpander's pressure boost end, another way lug connection plate heat exchanger to the lower column that exports the lug connection rectifying column that connects at this plate heat exchanger, it connects exit tube and pure liquid nitrogen to connect the exit tube to be provided with oxygen -enriched liquid air respectively at the lower column, oxygen -enriched liquid air connects exit tube and pure liquid nitrogen to connect exit tube lug connection in rectifying column upper column behind a subcooler, being provided with the liquid oxygen in the bottom of upper column and connecing the exit tube, this liquid oxygen meets exit tube intercommunication liquid oxygen storage tank.