The igneous reservoir take a very important role in the field of deep buried gas prospecting in Songliao basin. This paper take Xujiaweizi rift igneous gas reservoir as an example, applied micro heat-platform and laser Raman spectrum technology, probe in the fluid composition and impartial temperature characteristic of primary and secondary inclusion, it was discovered that there is a obviously difference in both fluid property and the composition of secondary inclusion is similar to that of reservoir natural gas, it proved that the impartial temperature of secondary package is able to reflect the natural gas reservoir forming period. Used secondary inclusion formed temperature combine with the analysis result of reservoir heat evolution history determined the individual well gas reservoir forming period. It shows that natural gas reservoir forming period of Huoshanling formation in Xujiweizi rift is 114~80 Ma, major period is 90~70 Ma, reservoir forming time is greater than 10 Ma in common, gas reservoir forming period is gradually tend to be more early from south to north of the rift; To Yingcheng formation, the natural gas reservoir forming period is 100~65 Ma, major period is 100~80 Ma, reservoir forming time is less than 10Ma in common, gas reservoir forming period is gradually tend to be more early form north to south of the rift. Natural gas reservoir forming period change in rift are related to the partition of the development of hydrocarbon source rock and the difference of the buried history, the distribution of source rock control the cross development of gas reservoir.