The main objective of this thesis is to determine the feature of auxiliaryverbs in modern Mongolian language and lists of auxiliary words, themeaning of each word, and its positions and roles in Mongolian language. In linguistics auxiliary verbs are rather similar to main verbs but havetheir own features that often attract linguistic researchers’ attention. Specially, the issue about auxiliary verbs weighs mainly in debates whichwas related to auxiliary verbs and main verbs. Any bigger studies onauxiliary verbs in linguistics can be done through Pagva’s independentresearch. Therefore, we aimed for detailed studies on the feature ofauxiliary verbs and tried to determine their specific meanings andimportance in the general research up until now. After setting up the objective, we evaluated studies on auxiliary verbs ofmodern Mongolian language up to the present and made list of auxiliaryverbs on a basis of own study category by using our evaluation andconclusion. We tried to unite and assess the studies on auxiliary verbs ofMongolian language. Moreover, we would like to determine our researchmethods and explain eight different types of features to distinguish themain verbs from auxiliary verbs. These features became the mainmeasurement to make distinction between auxiliary verbs and main verbs as well as the main study of this thesis. We used schemes to show thepositions of auxiliary verbs in sentences and explained plainly usingsentence structure. We provided examples on recognizing sentences withauxiliary verbs from sentences with combined verbs. Using eight features of the auxiliary verbs as starting points, wedetermined the features of auxiliary verbs to differ them from other verbsand listed auxiliary verbs studied by researchers and reviewed them withinour study. In addition, auxiliary verbs were categorized through a basis oftheir meanings and those with similar meanings were contrasted showingtheir similarity and dissimilarity. All the auxiliary verbs were classifieddepending on their linking suffixes and explained about the changes theyare making if there were any.