The research's first purpose is to analyze directly conservatism accounting influence towards book tax differences and tax avoidance. The second purpose is to analyse indirect influence towards tax avoidance through book tax differences. The research is conducted to companies enlisted in Indonesian Stock Exchange and belongs to LQ45 during 2013 to 2015. The number of companies sample taken by purposive sampling is 23 corporations, therefore total observation is 69 observations. The acquired data analysed by path analysis. This research conclude that conservatism accounting practice significantly influence book tax difference practice but did not influence tax avoidance. Conservatism accounting practice is also having no influence towards tax avoidance committed by book tax differences. This book tax difference is only significantly influential to commit tax avoidance. This research can contribute in taxation field as input in tax planning formulation.Page56 avoidance does not belong in the category of tax laws because the taxpayer's attempt to minimize or avoid the tax expense is committed by various ways made possible by tax laws. According to Finnerty, Merks, Petriccione, and Russo (2007), the ways that can be done for such things are: first, moving the tax subjects and or objects to countries that implement special treatment on tax or tax haven country on substantive tax planning. Second, tax avoidance attempt can be done through formal tax planning that give the taxpayer lowest tax expense. The third, by using anti-avoidance requirements towards transfer pricing, thin capitalization, treaty shopping, and controlled foreign corporation (specific anti avoidance rule), and transaction without business substance (general anti avoidance rule). In recent years, the tax authorites tried as hard as they can, not only to enforce clear boundaries between tax avoidance and tax evasion in tax planning, but also to prevent taxpayer from entering obscurity caused by tax laws (Bovi, 2005). With so many negative impacts caused by tax avoidance, research is needed to minimize the occurance, by investigating variables related to tax avoidance.