The methanol crossover across the proton exchange membrane in direct methanol fuel cells (DMFC) is one of the main problems in commercialization of DMFC, which has attracted a significant attention in DMFC researches. In this article, recent investigations of methanol crossover in DMFC were summarized from the viewpoints of the methanol transfer through Nafion membrane and the effect of the methanol crossover on the DMFC performance. The present research status in decreasing or overcoming the methanol crossover in DMFC was briefly reviewed in terms of the development of new types of solid electrolyte membranes with lower methanol permeability and new types of cathode catalysts. Some problems in researches of methanol crossover were pointed out by comparing different types of solid electrolyte membranes and cathode catalysts and their effect on methanol crossover. Future research directions in methanol crossover were suggested.