This paper describes the hydrogen and air premixedcombustion in a stainless steel tube of 1.66 millimeter in diameter.Temperature fields of combustor wall are measured with infrared thermometerand operating ranges of different combustors are obtained at differentthermal powers. With the help of recirculation zone in the facingback step,premixed combustion can be stabilized in the micro-combustor with a5\,mm-length facingback step and the maximum air excess coefficientis up to 1.415. But the premixed combustion can not be stabilized in thestainless steel tube without facingback step because of higher flow rate andgreat heat loss. It is proved that facingback step can steady the flame andenlarge the operating range for microscale combustion. The relation betweentemperature fields of combustor wall and air excess coefficient isreasonably interpreted by observing the shape and structure of the flame andanalyzing flow fields of combustor with facingback step. The resultscan be used in designs of the microscale combustor.