But when she forgot to turn up he set them off anyway hoping she would see them and go and see what was happening.
When Chien's girlfriend did not turn up he lit the fireworks anyway, hoping she would see them and come to see what was happening
Pal Shin Tan, 21, said: "He had prepared this big event in secret and had told her to meet him by the sports ground for a romantic walk.
"She had no idea he was planning to propose though, and clearly forgot all about the walk."
As firemen rushed to the scene to put out the three-metre high flames on the grass, gutted Chien went looking for forgetful Yen.
He said: "I was feeling a bit surprised that she hadn't shown up, and was completely unaware that the fireworks had set the grass on fire.
"When I found her I said she had to come with me as there was something important I wanted to tell her and show her.
"But as we approached the sports hall we saw all these flames and firemen and I decided to postpone the proposal to another date."
The flames which were up to three metres tall destroyed the sports hall
Bewildered Yen told local TV: "I found out later that he wanted to ask me to marry him.
"Of course, I love him, but my parents have told me to steer clear, saying he cant even ask me to marry him without causing a massive hoo-ha."
It took firemen over an hour to extinguish the blaze at the Liaoning Advertisement Vocational College in the city of Shenyang in north-eastern China's Liaoning province.
A college spokesman said: "The hall is covered by insurance and we have yet to make a decision about how to punish this student."