The invention provides membraneless fuel cell catalyst slurry and methods for preparing the catalyst slurry and an electrode. The catalyst slurry comprises a solid catalyst, a dispersing agent, a connecting material and an auxiliary. The preparation method of the catalyst slurry comprises the following steps: stirring and mixing the auxiliary, the connecting material and the dispersing agent to obtain paste type slurry; and then adding the catalyst into the paste type slurry during high-speed stirring, and stirring to obtain the evenly dispersed catalyst slurry. The invention further provides a preparation method of an electrode assembly. The slurry is good in dispersity and high in stability, not only can the catalyst agglomeration phenomenon be avoided, but also the usage amount of precious metal platinum can be reduced, and the catalyst can form a uniform and compact thin membrane on a substrate. The catalyst slurry and electrode assembly preparation methods are simple, convenient to operate, and strong in repeatability, and is suitable for continuous production, and the large-scale popularization and application is facilitated.