Le résumé en français n'a pas été communiqué par l'auteur. / This thesis deals with several theoretical subjects about optimal fiscal and government policy. It contains my four works about tax and other redistributive policy, starting with the general introductory survey as the first chapter. Chapter 2 compares ad-valorem and specific taxation in models where a representative consumer with an exogenous income has both a quality and a quantity choice under perfect competition. In the setting, while ad-valorem tax causes income effect only, specific tax causes both income effect and substitution effect. Therefore, advalorem tax decreases consumer demand for both quality and quantity; on the other hand, specific tax decreases consumer demand for quantity. However, the sign of consumer demand for quality is ambiguous and is determined by the curvature of marginal utility on quantity. Additionally, using a constant elasticity of substitution (CES) utility function and a linear price function, we show that ad-valorem tax is superior to specific tax except for the Leontief preference under which the two forms of commodity taxes generate the same tax revenue. The substitution effect caused by specific tax disappears if the elasticity of substitution converges to zero. In Chapter 3, We examine optimal taxation and public good provision by a government which takes reduction of envy into consideration as one of the constraints. We adopt the notion of extended envy-freeness proposed by Diamantaras and Thomson(1990), called λ-equitability. We derive the modified Samuelson rule at an optimum income tax, and show that, using a constant elasticity of substitution utility function, the direction of distorting the original Samuelson rule to relax λ envy free constraints is crucially determined by the elasticity of substitution. Furthermore, we numerically show that the level of public good increases (or decreases) in the degree of envy-freeness when the provision level is upwardly (or downwardly) distorted. Also,Chapter 4 covers the topic of public good provision under income transfer under that ethical constraint, but allows the social planner to set the surcharge fee for the purpose of excluding some agents whereas we simplify their income as exogenous one (or initial wealth). In this chapter, we study optimal public good provision and user fee in order to exclude some agents by Rawlsian or utilitarian government under lump-sum transfer, constrained by reduction of envy. In particular, we employ the exclusion technique used in Hellwig (2005), i.e., the policymaker decides the level of provision and surcharge fee paid by those making access to it, as well as uniform transfer. Different from Hellwig (2005), we introduce heterogeneity in initial wealth for agents and the envy-free constraint with respect to their one, but not to their tastes for public good. In this setting, we derive the optimal provision level and user fee, and compared to those in Hellwig (2005), for Rawlsian government, the up-charge is lower than the one derived in Hellwig (2005) in order to reduce the envy. Chapter 5 studies optimal nonlinear income tax schedule at symmetric equilibria at which two symmetric states (or tax authorities) compete in order to attract more tax-payers from the opposite. It is different from the existing papers that taxpayers’ wage are endogenously determined by production technology. The optimal tax schedule embraces not only migration effect, but also trickle-down effect coming from endogenous wage, and the migration effect stimulates the trickle-down effect. Compared to previous works, the threat of emigration never disappears in marginal tax rate for highskilled workers because emigration terms are embedded in the production and such factors have impacts on the productivities or their unit wages.