A papermaking process includes, firstly, providing carboxylated cellulosic fibers with a carboxyl group content being in the range from 0.06 to 1.5 mmol/g. Then the carboxylated cellulosic fibers are employed to prepare mixing pulp including filler particles, wherein the content of the carboxylated cellulosic fibers in the mixing pulp is in the range from 40% to 100% by dry fiber weight of the mixing pulp. After that, paper is made employing the mixing pulp.