如果本科成绩不算好，报考香港的大学的研究生有戏么？

本科成绩在研究生入学中不算最重要的，要确实是比较重要的
如果英文成绩很牛，并且有科研成果的话，会弥补你在GPA上的不足
但若一切都很平庸，那确实很困难
研究生专业我建议尽量和本科对口，除非经济学

You can change your major into economics, provided you have completed the following: introduction to economics, intermediate economics and advanced economics (all for theories), math (including linear algebra, matrix, calculus), statistics (including probability) and economometrics. Some may require furhter like economic history, economic development, monetary theory, macro economic theory.

Not a lot can qualify unless your first degree is in math, physics, engineering or closedly related social sciences.

经济学跨专业才没法申....这是常识...