Objective:To optimize the conditions for determination of the earthy and musty odors geosmin,2－methylisoborneol (2－MIB) in natural water by headspace solid－phase micro－extraction (SPME) coupled with gas chromatography/mass spectrometry and to establish a proposed method for determining the typical odor compounds in water. Methods:By applying the orthogonal experiment design L32(49) to arrange the determination conditions,several parameters of the extraction and desorption were studied and optimized (such as extraction temperature,desorption temperature,extraction time,ionic strength and rotate－speed),and some other parameters (such as correlation coefficient,limits of detection,RSD and recovery) were applied to evaluate effect of this method. Results:The optimum temperature of extraction and desorption were 65℃ and 260℃,respectively;time of extraction and desorption were 40 min and 7 min,respectively;ionic strength,30%(W/V);rotate－speed,600 rpm. Under the optimized experimental conditions,limits of detection(S/N=3) were 0.04 and 0.42 ng/L for geosmin and MIB,respectively. Calculated calibration curves gave high levels of linearity with correlation coefficient values of 0.9999 for both of geosmin and MIB. Finally,the proposed method was applied to the analysis of seven standard water samples,which were previously analyzed and confirmed free of target analytes. The RSD were 2.75%~3.80% and 4.35%~7.6% for geosmin and 2－MIB,respectively,and the recovery values were 91%~107% and 91%~104% for geosmin and MIB,respectively. Conclusion:The method can be successfully applied to analyze earthy and musty odors in natural water.