Am I eligible to travel to the US with my UN 1951 Travel Document issued by Malta (EU)?

To use the US Visa Waiver Program, you must be a citizen or national of one of the listed countries.

This requirement is documented on the Department of State web site:

You must be a citizen or national of VWP-participant country.

Further on the Customs and Border Protection web site:

Citizens or nationals of the following countries are currently eligible to travel to the United States under the VWP:

So unfortunately you will need a visa.

Normally this would not be difficult to get, but a notice on the US Embassy in Malta's web page states that they are having technical difficulties with visa processing and that visas may be delayed.

The Department of State’s Bureau of Consular Affairs is currently experiencing technical problems with our overseas passport and visa systems. This issue is not specific to any particular country, citizenship document, or visa category. We apologize for the inconvenience and are working urgently to correct the problem and restore full operability.

Which, I suspect, may be part of the reason you asked this question.

The US government's web sites (of the Department of State and of the Customs and Border Protection Agency) don't give explicit information about this, surprisingly. The US law code is unambiguous, however. Title 8, section 1187, paragraph (a) (2):

The alien is a national of, and presents a passport issued by, a country which—

Therefore, you must be a citizen of one of the VWP countries, and you must travel on a passport issued by that country. (This means that a citizen of VWP country A who lives as a refugee in VWP country B would require a visa to travel with the a refugee document issued by B.)

No you are not.

For all intents and purposes, including Visa Waiver Program, you're not a national of Malta. You're either a Chinese national or a stateless person that is a resident of Malta.

Usually the refugee documents will have a different "Passport Type" from the normal "P" for the ordinary passports.

I don't know exactly what the rules for people travelling on a refugee travel document are in the US but the visa waiver program is based strictly on citizenship and you are not a Maltese citizen. It's therefore likely that you need a visa.

You might not have a Chinese passport but still be considered a Chinese citizen (at least it seems to be the case as far as Malta is concerned). If you really did lose your Chinese citizenship, you could also conceivably be stateless (although in this case, you would typically have another document) but the fact that you reside in Malta and hold a Maltese travel document does not make you eligible for the VWP.