Exhibit 99.1

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) promulgated under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree to the joint filing with all other Reporting Persons (as such term is defined in the Schedule 13G referred to below) on behalf of each of them of a statement on Schedule 13G (including amendments thereto) with respect to the Class B ordinary shares, par value US$0.001 per share, of Gridsum Holding Inc., a Cayman Islands company, and that this Agreement may be included as an exhibit to such joint filing. This Agreement may be executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.

IN WITNESS WHEREOF, the undersigned hereby execute this Agreement as of June 4, 2019.

Hammer Capital Private Investments Limited
By:	/s/ Cheung Siu Fai
	Cheung Siu Fai
	Director
Tsang Ling Kay Rodney
/s/ Tsang Ling Kay Rodney
Hammer Capital China Limited
By:	/s/ Cheung Siu Fai
	Cheung Siu Fai
	Director
Cheung Siu Fai
/s/ Cheung Siu Fai