The immune activation and toxicity of fresh Cordyceps militaris extracts (HFCM) treated by high-pressure processing (HPP) were evaluated by spleen and thymus index, macrophages phagocytosis activity, lymphocyte proliferation, interleukin-2, interferon-γ level, and human kidney 293 cells, hepatic and kidney function, with the ultrasonic treatment as control (UFCM). The results showed the spleen and thymus index, macrophage function, lymphocyte proliferation, IL-2, and IFN-γ levels in HFCM groups were higher than that in UFCM groups by 11.45-12.43%, 11.52-13.95%, 8.92-11.05%, 8.98-9.23%, 9.3-12.66%, and 12.69-17.83%. HFCM was 21.97%, 21.5%, and 20.74% higher than UFCM in the contents of polysaccharide, cordycepin, and total flavonoids. HFCM showed no toxicity to the cell viability, kidney, and hepatic, while the cell viability in UFCM groups was decreased to 81.54%. So the HFCM was stronger than UFCM in immune activation with no toxicity, and can be used as fresh health food.