Thermal emission is often presented as a typical incoherent process.Incorporating periodic structures on the tungsten surface offers the possibility to obtain coherent thermal emission sources.Here we illustrate grating as an example to examine the influence of the geometric parameters on the thermal emission properties.It is found that for very shallow gratings,only surface plasmon polariton (SPP) modes can be excited and the emission efficiency is closely related with the filling factor.When the ratio of the depth to period of the grating is in the range from 1/20 to 1/2,the field between the adjacent coers can be coupled to each other across the air gap for the filling factor larger than 0.5 and produce a similar resonance as in an air rod.Further increase of the grating depth can cause the groove of the grating forming metalinsulator-metal (MIM) structures and induce surface plasmon standing wave modes.Our investigations will not only be helpful for manipulating thermal emission properties according to applications,but also help us understand the coupling mechanism between the incident electromagnetism waves and gratings with different parameters in various research fields.