She gave a speech Monday at a Beijing university ahead of a China-EU summit Tuesday and Wednesday.
The EU accuses China of dumping cheap steel on European markets, accusations denied by China.
Cecilia Malmstrom says market access and other issues need to be ironed out first to establish "a more level playing field".
The investment will also mark a deepening of Sino-EU economic ties, after European governments signed up to the Chinese-led Asian Infrastructure Investment Bank (AIIB), despite Washington's displeasure, part of China's so-called chequebook diplomacy to win greater influence.
A White House spokesman congratulated May on her new position, adding that President Barack Obama was hoping for an "orderly process and a good-faith negotiation between the United Kingdom and the EU".
Jean Claude Juncker, president of the European Commission.
Mogherini said Europe is China's biggest trading partner, while China is the EU's second biggest.
Addressing several hundred executives and government representatives at a business meeting Wednesday on the sidelines of the summit, Mr. Li defended China against charges it is exporting steel and other commodities below their cost.
Under the so-called "One Belt, One Road" initiative, China aims to create a modern Silk Road Economic Belt and a 21st Century Maritime Silk Road to boost trade and extend its global influence.
"The EU will defend its steel industry". Leave campaigners heavily criticised the European Union in the run-up to the referendum for failing to put tariffs on Chinese steel exports and not doing enough to help the industry.
"Although we feel that in the short term, Brexit will impact on the British economy and thus will impact the global economy to some extent, we think that in a few years from now there will be no remaining consequences on the global economy", Juncker said.
The annual EU-China summit has become a key fixture on the global calendar, bringing together leaders from two of the world's largest traders for talks on a wide-ranging agenda that often includes topics such as climate change, investment, trade, and human rights.
ICTSD reporting; "China vows to curb overcapacity in steel", DEUTSCHE WELLE, 13 July 2016; "China agrees European Union deal to assuage steel dumping concerns", FINANCIAL TIMES, 13 July 2016. Juncker also announced the setting up of a common working group that discuss the issue of steel overproduction.