The spreading angle of a near-critical RP-3 kerosene jet into a quiescent subcritical nitrogen chamber through a simple injector was experimentally investigated through a schlieren imaging system. The jet spreading angles affected by ambient pressure, injection pressure, and injection temperature are separately analyzed. It is found that the jet spreading angle increases with the increased injection pressure, but decreases with increased injection temperature. However, the jet spreading angle shows an unusual drastic changing trend when the ambient pressure is just from 2.5 to 3.0 MPa. These phenomena are analyzed based on the injection dynamics and injectant physical proprieties. It is believed that the sensitivity of the physical properties of the injectant in near-critical condition is responsible for the drastic changing trends of the jet spreading angle. The momentum of the injectant is a dominating factor instead of the density ratio that affects the jet spreading angle under this experimental condition.