1. College of Earth Sciences，Jilin University，Changchun 130061，China; 2. SINOPEC Northeast Company，Changchun 130062，China

The pyroclastic rocks of the Huoshiling Formation have been proven as effective hydrocarbon reservoirs in the Longfengshan area，Changling fault depression，southern Songliao Basin． In this paper，the features and controlling factors of reservoir spaces have been analyzed based on the typical sections of the pyroclastic rocks of six wells from the Huoshiling Formation． Based on the results of drilling core observation，blue-dye thin section and scanning electron microscope ( SEM) analysis，and porosity and permeability test，it can be concluded that，the pyroclastic rocks are mainly composed of andesitic pyroclastic rocks and pyroclastic lava，and their corresponding lithofacies is dominated by air-fall subfacies of explosive facies． The tuffaceous cemented volcanic breccias show a top reservoir quality with porosities ranging from 3. 86% to 8. 76% and an average permeability of 0. 397 ×10 － 3 μm2 ． During the process of later diagenesis，most of the primary reservoir spaces have been filled up，and the secondary pores and fractures formed by dissolution and tectonism have contributed the main body of the current effective reservoir spaces，which mainly existed as the combination of reticular microfractures and dissolution micro-holes．