Go through your results for flights to Harbin in China with Netflights. Although Air China usually has the best prices, it's best to double check what's available for your travel dates.
Flexible on dates? Conducting your search by month allows you to compare prices to Harbin throughout the year. For example, prices will almost certainly be higher around August, as this is peak season in Harbin. Accommodation prices will also be higher at this time of year. Flights to Harbin are usually cheapest in June.
Look out for flights with Air China, as they often have good deals. Or broaden your search by looking at other airports in China.
Looking at a few different departure airports will give you even more choice. See what you can find. And remember, it's best to book your flights in advance wherever possible.