一、澳大利亚国旗：长方形，长宽之比为2：1。
The ratio of length to width of the Australian flag is 2:1.
二、左上角为大不列颠及北爱尔兰联合王国国旗，表明澳大利亚联邦与英国的传统关系。
The upper left corner is the flag of the United Kingdom of Great Britain and Northern Ireland, which indicates the traditional relationship between the Commonwealth of Australia and the United Kingdom.
三、靠旗杆侧上角有英国米字旗，靠旗杆侧下部有一颗白色的七角星。
On the upper corner of the flagpole there is a British meter-shaped flag and on the lower side there is a white heptagonal star.
四、最大的一颗七角星代表的是澳大利亚联邦的六个州与一个区，蓝色象征着大海环抱着澳大利亚联邦领土。
The largest seven-pointed star represents six states and one region of the Commonwealth of Australia. Blue symbolizes the sea encircling the territory of the Commonwealth of Australia.
五、由英国国王爱德华七世在1904年选定的。
Selected by King Edward VII of England in 1904.
参考资料来源：百度百科-澳大利亚国旗
The flag of Australia is a defaced Blue Ensign: a blue field with the Union Flag in the canton (upper hoist quarter), and a large white seven-pointed star known as the Commonwealth Star in the lower hoist quarter. The fly contains a representation of the Southern Cross constellation, made up of five white stars – one small five-pointed star and four, larger, seven-pointed stars.
The flag's original design (with a six-pointed Commonwealth Star) was chosen in 1901 from entries in a worldwide competition held following Federation, and was first flown in Melbourne on 3 September 1901;this date has been proclaimed as Australian National Flag Day. A slightly different design was approved by King Edward VII in 1902. Over the next few years, the exact specifications of the flag were changed several times both intentionally and as a result of confusion. The current specifications were formally gazetted in 1934, and in 1954 the flag became recognised by, and legally defined in, the Flags Act 1953, as the "Australian National Flag".
本回答被提问者和网友采纳国旗的左上角为英国国旗图案，表明澳洲与英国的传统关系。最大的一颗七角星代表的是澳洲的六个州与一个区，蓝色象征着大海环抱着澳洲领土。
这面旗帜是从一次设计比赛中，由英国君主在1904年选定的。最初这面旗帜主要用于海军的军旗，而米字旗才是更常用的国家象征。1954年英国女王访问澳洲时正式确定这面旗帜为澳洲的国旗，但直到1960年代，这面旗帜才完全取代米字旗，成为国家的象征。
有一些澳洲人对于旗帜上的米字旗感到不满，而该旗与新西兰国旗十分相似，也常常被混淆。但目前这面国旗还是受到大多数人的支持，而且在澳洲共和制争议被完全解决之前，这面旗帜还不太可能被另一面旗帜替换。