With the increasingly large scale of immersed elements and caissons，the effects of wake flows of towing vessels cannot be ignored, but relative research is very few in China at present. Based on the calculation method of propeller slip stream recorded in foreign literatures，the range of influence of wake streams and the velocity of wake streams is analyzed，and the acting force of the propeller slipstream on the immersed elements or caissons is calculated，providing some basis for calculating of floating transportation of caissons and elements.