In this paper, a simplified time-of-flight fluorescence imaging method is introduced for measuring the effective temperature of cold atom sample. The cooling laser for laser cooling and trapping atoms instead of the additional probe laser of standard time-of-flight fluorescence imaging. Based on the magneto-optical trap of cesium atom, the effective temperature of cold atoms is effectively reduced by using the technique of polarization gradient cooling. The effective temperature measurement of cesium atomic MOT (molasses) by means of simplified time-of-flight fluorescence imaging, with typical values are TY≈22.3±2.2K and TZ≈15.4±2.7K (TY≈11.6±1.1K and TZ≈2.8±1.2K). The simplified time-of-flight fluorescence imaging scheme proposed in this paper is easier to execution and promotion in experiments, without sacrificing the precision and accuracy of effective temperature measurement of the cold atom sample. It has positive significance and good promotion value for the application of cold atom microwave atomic clock, cold atom optical frequency atomic clock, cold atom gravimeter and other quantum precision measurement fields, as well as the further development of quantum optics and quantum information processing by using cold atom sample.