Colin Huang was valued at $45.4bn (£36.4bn) by Forbes, on Sunday, ahead of Alibaba's Jack Ma but behind Tencent's Pony Ma.
Mr Huang was previously an intern at Microsoft and then spent three years as an engineer at Google.
“These three years were incredibly valuable to me,” he blogged in 2016.
“Google gave me far more than I contributed.”
According to Forbes, a slip in Pinduoduo's value has since given Mr Ma back the second spot.
Mr Huang founded Pinduoduo in 2015.