We are a group of four people with four big luggage need a taxi to downtown Harbin

The taxi in China in general can only hold 4 passengers. But I'm afraid that there is enough space for 4 pieces of luggage.
You are advised to book a larger one in advance on eHi Car Service.

You need to rent a van, last time my visit here i rent a buick GL-8, so my four big luggage and all my group of 4 adults can fit comfortably in. Price was 300 CNY from airport to IBIS Hotel at Normal University - using local travel biro rentcar service - they can communicate by wechat - which has facility english to chinese translation - but they can not speak verbal english . Price is higher from english speaking service as one easily searchable on internet.