An experimental investigation using electric heating method is carried out to explore the effect of tilt angle and heat flux on heat losses of a fully opened cylindrical cavity receiver. Two cases are examined,i.e. all walls of cavity heated and only the bottom wall (opposite wall of opening)heated. For both cases,the walls are heated at a constant heat flux. The empirical correlations of Nusselt numbers of natural convection and radiation heat losses versus the Grashof number,tilt angle and corresponding heat loss flux are proposed. The results show that,with constant input power,the natural convection heat loss of receiver decreases as the tilt angle increases while the conduction heat loss and the radiation heat loss increase slightly. When the heat flux of natural convection heat loss keeps constant,Nusselt number for determining the natural convection heat loss reduces with increasing tilt angle. However,when the heat flux of radiation heat loss remains constant,the tilt angle has very little effect on the Nusselt number for determining the radiation heat loss. Also,there is a certain difference of heat loss performance between two cases,and the wall heating location has a relatively samll influence on the radiation heat loss in comparison with on the natural convection heat loss.