An assembly method for display panel comprises the following steps. First, a first substrate and a second substrate are placed inside a chamber, wherein the first substrate comprises a sealant disposed thereon, and the chamber has a first pressure. Next, the pressure inside the chamber is adjusted to a second pressure, which is lower than the first pressure. After that, the first substrate is aligned with the second substrate, and the second substrate is placed on the sealant, to form a closed space between the first substrate and the second substrate. The pressure inside the closed space is the second pressure. Thereafter, the chamber is pumped from the second pressure to a third pressure, to bond the first substrate and the second substrate together by the pressure difference between the third pressure of the chamber and the second pressure of the closed space. Finally, the sealant is cured.