Zhang's wealthiest clients include the owners of coal-mines which dot the landscape of northern China, he said.
"Now almost everyone has a car, so people need a new way of showing their wealth," he said, adding that not all of his clients pay in cash.
"One buyer paid for a dog with a 30,000 yuan Omega watch and a car, just for a small dog," he said, whipping out his smartphone to show a record of the transaction.
The sperm of pure-bred mastiffs can also be worth a fortune. "I would charge 50,000 yuan to sell his sperm," Zhang said of his favourite dog, named "Moonlight Fairytale", on sale for 200,000 yuan and weighing 155 kilogrammes (340 pounds).
The booming market has attracted a fair share of fraudsters, with some passing off crossbred dogs for pedigrees, using artificial hair extensions made with dog fur, the China Daily reported.
Intensive breeding has led to dangerous numbers of inbred mastiffs, while some vendors inject glucose into dog's legs to make them appear stronger, the Global Times daily reported.