This article introduces the principle and formation of hardwares and softwares of Full Range CH4 Surveying Meter used in mines.This kind of instrument can survey CH4 density ranging from zero to 100 percent.D to the adoption of the new- type chip computer PIC16C57 and I2CBOS series connection I/O technique,the meter,s revising the non- linearity of the heat conductive element,the surveying result become more accurate.