CAS, Inst High Energy Phys, Beijing 100039, Peoples R China
; Yunnan Univ, Dept Phys, Kunming 650091, Peoples R China
; SW Jiaotong Univ, Chengdu 610031, Peoples R China
TeV GRBs are so far only searched by EAS arrays which typically have an angular resolution at about 1degrees. With the limited power in identifying gamma ray events from proton background events, a search window in the size of angular resolution is often chosen in many experiments. In attempting to optimize the average search sensitivity, an analytic method to determine the window size is proposed and verified by Monte Carlo method in various conditions, including different signal, background intensities and different significance calculation methods. Finally, at the situation of low statistics, an empirical significance calculation formula seems to be possible.